Interlingua
interlingua
Logo
Pronunciation	[inteɾˈliŋɡwa]
Created by	International Auxiliary Language Association
Date	1951
Setting and usage	Scientific registration of international vocabulary; international auxiliary language
Users	A few hundred (2007)[1]
Purpose	International auxiliary language Interlingua
Writing system	Latin script
Sources	Source languages: English, French, Italian, Portuguese, and Spanish.
Official status
Regulated by	No regulating body
Language codes
ISO 639-1	ia
ISO 639-2	ina
ISO 639-3	ina
Glottolog	inte1239
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Interlingua (/ɪntərˈlɪŋɡwə/, Interlingua: [inteɾˈliŋɡwa]) is an international auxiliary language (IAL) developed between 1937 and 1951 by the American International Auxiliary Language Association (IALA). It is a constructed language of the "naturalistic" variety, whose vocabulary, grammar, and other characteristics are derived from natural languages. Interlingua literature maintains that (written) Interlingua is comprehensible to the billions of people who speak Romance languages,^[2] though it is actively spoken by only a few hundred.^[1]

Interlingua was developed to combine a simple, mostly regular grammar with a vocabulary common to a wide range of western European languages, making it easy to learn for those whose native languages were sources of Interlingua's vocabulary and grammar.^[3][4]

The name Interlingua comes from the Latin words inter, meaning 'between', and lingua, meaning 'tongue' or 'language'. These morphemes are the same in Interlingua; thus, Interlingua would mean 'between language'.

Interlingua focuses on common vocabulary shared by Western European languages, which are often descended from or heavily influenced by the Latin language (such as the Romance languages) and Greek language. Interlingua organizers have four "primary control languages" where, by default, a word (or variant thereof) is expected to appear in at least three of them to qualify for inclusion in Interlingua. These are English; French; Italian; and a combination of Spanish and Portuguese which are treated as a single mega-language for Interlingua purposes, as both are west Iberian languages. Additionally, German and Russian have been dubbed "secondary control languages".^[3] While the result is often akin to Neo-Latin as the most frequent source of commonality, Interlingua words can have origins in any language, as long as they have drifted into the primary control languages as loanwords. For example, the Japanese words geisha and samurai and the Finnish word sauna are used in most Western European languages, and therefore in Interlingua as well; similarly, the Guugu Yimithirr word gangurru is used in latinized form (Interlingua: kanguru, English: kangaroo).^[3]

The maintainers of Interlingua attempt to keep the grammar simple and word formation regular, and use only a small number of roots and affixes. This is intended to make the language quicker to learn.^[5]

The American heiress Alice Vanderbilt Morris (1874–1950) became interested in linguistics and the international auxiliary language movement in the early 1920s. In 1924, Morris and her husband, Dave Hennen Morris, established the non-profit International Auxiliary Language Association (IALA) in New York City. Their aim was to place the study of IALs on a more complex and scientific basis. Morris developed the research program of IALA in consultation with Edward Sapir, William Edward Collinson, and Otto Jespersen.^[6]

Investigations of the auxiliary language problem were in progress at the International Research Council, the American Council on Education, the American Council of Learned Societies, the British, French, Italian, and American Associations for the advancement of science, and other groups of specialists. Morris created IALA as a continuation of this work.^[7]

The IALA became a major supporter of mainstream American linguistics. Numerous studies by Sapir, Collinson, and Morris Swadesh in the 1930s and 1940s, for example, were funded by IALA. Alice Morris edited several of these studies and provided much of IALA's financial support.^[7] For example, Morris herself edited Sapir and Morris Swadesh's 1932 cross-linguistic study of ending-point phenomena, and Collinson's 1937 study of indication. IALA also received support from groups such as the Carnegie Corporation, the Ford Foundation, the Research Corporation, and the Rockefeller Foundation.^[8][9]

In its early years, IALA concerned itself with three tasks: finding other organizations around the world with similar goals; building a library of books about languages and interlinguistics; and comparing extant IALs, including Esperanto, Esperanto II, Ido, Peano's Interlingua (Latino sine flexione), Novial, and Interlingue (Occidental). In pursuit of the last goal, it conducted parallel studies of these languages, with comparative studies of national languages.^[7]

At the Second International Interlanguage Congress, held in Geneva in 1931, IALA began to break new ground; 27 recognized linguists signed a testimonial of support for IALA's research program. An additional eight added their signatures at the third congress, convened in Rome in 1933.^[10] That same year, Herbert N. Shenton and Edward Thorndike became influential in IALA's work by authoring studies in the interlinguistic field.^[7]

The first steps towards the finalization of Interlingua were taken in 1937, when a committee of 24 linguists from 19 universities published Some Criteria for an International Language and Commentary. However, the outbreak of World War II in 1939 cut short the intended biannual meetings of the committee.^[11]

Originally, the association had not intended to create its own language. Its goal was to identify which auxiliary language already available was best suited for international communication, and how to promote it more effectively. However, after ten years of research, many members of IALA concluded that none of the existing interlanguages were up to the task. By 1937, the members had made the decision to create a new language, to the surprise of the world's interlanguage community.^[12]

To that point, much of the debate had been equivocal on the decision to use naturalistic (e.g., Peano's Interlingua, Novial and Occidental) or systematic (e.g., Esperanto and Ido) words. During the war years, proponents of a naturalistic interlanguage won out. The first support was Thorndike's paper; the second was a concession by proponents of the systematic languages that thousands of words were already present in many, or even a majority, of the European languages. Their argument was that systematic derivation of words was a Procrustean bed, forcing the learner to unlearn and re-memorize a new derivation scheme when a usable vocabulary was already available. IALA from that point assumed the position that a naturalistic language would be best.^[9]

IALA's research activities were based in Liverpool, before relocating to New York due to the outbreak of World War II, where E. Clark Stillman established a new research staff.^[7] Stillman, with the assistance of Alexander Gode, constructed the methodology for selecting Interlingua vocabulary based on a comparison of control languages.^[9]

In 1943 Stillman left for war work and Gode became Acting Director of Research.^[7] IALA began to develop models of the proposed language, the first of which were presented in Morris's General Report in 1945.^[12]

From 1946 to 1948, French linguist André Martinet was Director of Research. During this period IALA continued to develop models and conducted polling to determine the optimal form of the final language. In 1946, IALA sent an extensive survey to more than 3,000 language teachers and related professionals on three continents.^[9][13]

Model P was unchanged from 1945; Model M was relatively modern in comparison to more classical P. Model K was slightly modified in the direction of Ido. The resulting four models that were canvassed were:^[9]

An example sentence:

The vote total ended up as follows: P 26.6%, M 37.5%, C 20%, and K 15%.^[14] The two more schematic models, C and K, were rejected. Of the two naturalistic models, M attracted somewhat more support than P. Taking national biases into account (for example, the French who were polled disproportionately favored Model M), IALA decided on a compromise between models M and P, with certain elements of C.^[13]

The German-American Gode and the French Martinet did not get along.^[15] Martinet resigned and took up a position at Columbia University in 1948, and Gode took on the last phase of Interlingua's development.^[7] His task was to combine elements of Model M and Model P; take the flaws seen in both by the polled community and repair them with elements of Model C as needed; and develop a vocabulary. Alice Vanderbilt Morris died in 1950, and the funding that had sustained IALA ceased, but sufficient funds remained to publish a dictionary and grammar.^[15] The vocabulary and grammar of Interlingua were first presented in 1951, when IALA published the finalized Interlingua Grammar and the Interlingua–English Dictionary (IED). In 1954, IALA published an introductory manual entitled Interlingua a Prime Vista ("Interlingua at First Sight").

Interlingua as presented by the IALA is very close to Peano's Interlingua (Latino sine flexione), both in its grammar and especially in its vocabulary. A distinct abbreviation was adopted: IA instead of IL.

An early practical application of Interlingua was the scientific newsletter Spectroscopia Molecular, published from 1952 to 1980.^[16] In 1954, the Second World Cardiological Congress in Washington, D.C. released summaries of its talks in both English and Interlingua. Within a few years, it found similar use at nine further medical congresses. Between the mid-1950s and the late 1970s, some thirty scientific and medical journals provided article summaries in Interlingua.^[17] Gode wrote a monthly column in Interlingua in the Science Newsletter published by the Science Service from the early 1950s until his death in 1970.

IALA closed its doors in 1953 but was not formally dissolved until 1956 or later.^[18] Its role in promoting Interlingua was largely taken on by Science Service,^[13] which hired Gode as head of its newly formed Interlingua Division.^[19] Hugh E. Blair, Gode's close friend and colleague, became his assistant.^[20] A successor organization, the Interlingua Institute,^[21] was founded in 1970 to promote Interlingua in the US and Canada. The new institute supported the work of other linguistic organizations, made considerable scholarly contributions and produced Interlingua summaries for scholarly and medical publications. One of its largest achievements was two immense volumes on phytopathology produced by the American Phytopathological Society in 1976 and 1977.^[18]

Beginning in the 1980s, UMI has held international conferences every two years (typical attendance at the earlier meetings was 50 to 100) and launched a publishing programme that eventually produced over 100 volumes.^[22][23] Several Scandinavian schools undertook projects that used Interlingua as a means of teaching the international scientific and intellectual vocabulary.^[24]

In 2000, the Interlingua Institute was dissolved amid funding disputes with the UMI; the American Interlingua Society, established the following year, succeeded the institute.^[21]

The original goal of an interlanguage meant for global events has faced competition from English as a lingua franca and International English in the 21st century. The scientific community frequently uses English in international conferences and publications, for example, rather than Interlingua. However, the rise of the Internet has made it easier for the general public with an interest in constructed languages to learn Interlingua. Interlingua is promoted internationally by the Union Mundial pro Interlingua. Periodicals and books are produced by national organizations, such as the Societate American pro Interlingua, the Svenska Sällskapet för Interlingua, and the Union Brazilian pro Interlingua.^[21]

Panorama In Interlingua is the most prominent of several Interlingua periodicals. It is a 28-page magazine published bimonthly that covers current events, science, editorials, and Interlingua.

It is not certain how many people have an active knowledge of Interlingua. ^[9] Most constructed languages other than Esperanto have very few speakers.^[25] The Hungarian census of 2001, which collected information about languages spoken, found just two people in the entire country who claimed to speak Interlingua.^[26]

Advocates say that Interlingua's greatest advantage is that it is the most widely understood international auxiliary language besides Interlingua (IL) de A.p.I.^[27] by virtue of its naturalistic (as opposed to schematic) grammar and vocabulary, allowing those familiar with a Romance language, and educated speakers of English, to read and understand it without prior study.^[27]

Interlingua web pages include editions of Wikipedia and Wiktionary, and a number of periodicals, including Panorama in Interlingua from the Union Mundial pro Interlingua (UMI).

Every two years, the UMI organizes an international conference in a different country. In the year between, the Scandinavian Interlingua societies co-organize a conference in Sweden, as a number of Interlingua speakers are in Scandinavia. National organizations such as the Union Brazilian pro Interlingua also organize regular conferences.^[24]

Interlingua is taught in some high schools and universities, sometimes as a means of teaching other languages quickly, presenting interlinguistics, or introducing an international vocabulary.^[24][28][29] A two-week course was taught at the University of Granada in Spain in 2007, for example.^[30]

As of 2019, Google Keyboard supports Interlingua.^[31]

Interlingua has a largely phonemic orthography.

Interlingua uses the 26 letters of the ISO basic Latin alphabet with no diacritics.^[32] The alphabet, pronunciation in IPA and letter names in Interlingua are:

The book Grammar of Interlingua defines in §15 a "collateral orthography"^[33] that defines how a word is spelt in Interlingua once assimilated regardless of etymology.

Interlingua is primarily a written language, and the pronunciation is not entirely settled. The sounds in parentheses are not used by all speakers.

For the most part, consonants are pronounced as in English, while the vowels are like Spanish. Written double consonants may be geminated as in Italian for extra clarity or pronounced as single as in English or French. Interlingua has five falling diphthongs, /ai/, /au/, /ei/, /eu/, and /oi/,^[34] although /ei/ and /oi/ are rare.

The general rule is that stress falls on the vowel before the last consonant (e.g., lingua, 'language', esser, 'to be', requirimento, 'requirement') ignoring the final plural -(e)s (e.g. linguas, the plural of lingua, still has the same stress as the singular), and where that is not possible, on the first vowel (via, 'way', io crea, 'I create'). There are a few exceptions, and the following rules account for most of them:

• Adjectives and nouns ending in a vowel followed by -le, -ne, or -re are stressed on the third-last syllable (fragile, margine, altere 'other', but illa impone 'she imposes').
• Words ending in -ica/-ico, -ide/-ido and -ula/-ulo, are stressed on the third-last syllable (politica, scientifico, rapide, stupido, capitula, seculo 'century').
• Words ending in -ic are stressed on the second-last syllable (cubic).

Speakers may pronounce all words according to the general rule mentioned above. For example, kilometro is acceptable, although kilometro is more common.^[35]

Interlingua has no explicitly defined phonotactics. However, the prototyping procedure for determining Interlingua words, which strives for internationality, should in general lead naturally to words that are easy for most learners to pronounce. In the process of forming new words, an ending cannot always be added without a modification of some kind in between. A good example is the plural -s, which is always preceded by a vowel to prevent the occurrence of a hard-to-pronounce consonant cluster at the end. If the singular does not end in a vowel, the final -s becomes -es.^{[citation needed]}

Unassimilated foreign loanwords, or borrowed words, are spelled as in their language of origin. Their spelling may contain diacritics, or accent marks. If the diacritics do not affect pronunciation, they are removed.^[3]

Words in Interlingua may be taken from any language,^[36] as long as their internationality is verified by their presence in seven control languages: Spanish, Portuguese, Italian, French, and English, with German and Russian acting as secondary controls. These are the most widely spoken Romance, Germanic, and Slavic languages, respectively. Because of their close relationship, Spanish and Portuguese are treated as one unit. The largest number of Interlingua words are of Latin origin, with the Greek and Germanic languages providing the second and third largest number. The remainder of the vocabulary originates in Slavic and non-Indo-European languages.^[3]

A word, that is a form with meaning, is eligible for the Interlingua vocabulary if it is verified by at least three of the four primary control languages. Either secondary control language can substitute for a primary language. Any word of Indo-European origin found in a control language can contribute to the eligibility of an international word.^[37] In some cases, the archaic or potential presence of a word can contribute to its eligibility.

A word can be potentially present in a language when a derivative is present, but the word itself is not. English proximity, for example, gives support to Interlingua proxime, meaning 'near, close'. This counts as long as one or more control languages actually have this basic root word, which the Romance languages all do. Potentiality also occurs when a concept is represented as a compound or derivative in a control language, the morphemes that make it up are themselves international, and the combination adequately conveys the meaning of the larger word. An example is Italian fiammifero (lit. 'flamebearer'), meaning 'match, lucifer', which leads to Interlingua flammifero, or 'match'. This word is thus said to be potentially present in the other languages although they may represent the meaning with a single morpheme.^[3]

Words do not enter the Interlingua vocabulary solely because cognates exist in a sufficient number of languages. If their meanings have become different over time, they are considered different words for the purpose of Interlingua eligibility. If they still have one or more meanings in common, however, the word can enter Interlingua with this smaller set of meanings.^[37]

If this procedure did not produce an international word, the word for a concept was originally taken from Latin (see below). This only occurred with a few grammatical particles.

The form of an Interlingua word is considered an international prototype with respect to the other words. On the one hand, it should be neutral, free from characteristics peculiar to one language. On the other hand, it should maximally capture the characteristics common to all contributing languages. As a result, it can be transformed into any of the contributing variants using only these language-specific characteristics. If the word has any derivatives that occur in the source languages with appropriate parallel meanings, then their morphological connection must remain intact; for example, the Interlingua word for 'time' is spelled tempore and not *tempus or *tempo in order to match it with its derived adjectives, such as temporal.^[38]

The language-specific characteristics are closely related to the sound laws of the individual languages; the resulting words are often close or even identical to the most recent form common to the contributing words. This sometimes corresponds with that of Vulgar Latin. At other times, it is much more recent or even contemporary. It is never older than the classical period.^[37]

The French œil, Italian occhio, Spanish ojo, and Portuguese olho appear quite different, but they descend from a historical form oculus. German Auge, Dutch oog and English eye (cf. Czech and Polish oko, Russian and Ukrainian око (óko)) are related to this form in that all three descend from Proto-Indo-European *okʷ. In addition, international derivatives like ocular and oculista occur in all of Interlingua's control languages.^[27] Each of these forms contributes to the eligibility of the Interlingua word.^[37] German and English base words do not influence the form of the Interlingua word, because their Indo-European connection is considered too remote.^[39] Instead, the remaining base words and especially the derivatives determine the form oculo found in Interlingua.^[27]

Words can also be included in Interlingua by deriving them using Interlingua words and affixes; a method called free word-building. Thus, in the Interlingua–English Dictionary (IED), Alexander Gode followed the principle that every word listed is accompanied by all of its clear compounds and derivatives, along with the word or words it is derived from. A reader skimming through the IED notices many entries followed by large groups of derived and compound words. A good example is the Interlingua word nation, which is followed by national, nationalismo, nationalista, nationalitate, nationalisar, international, internationalitate, and many other words.

Other words in the IED do not have derivatives listed. Gode saw these words as potential word families. Although all derived words in the IED are found in at least one control language, speakers may make free use of Interlingua roots and affixes. For example, jada ('jade') can be used to form jadificar, ('to jadify, make into jade, make look like jade'), jadification, and so on. These word forms would be impermissible in English but would be good Interlingua.

Gode and Hugh E. Blair explained in the Interlingua Grammar that the basic principle of practical word-building is analogical. If a pattern can be found in the existing international vocabulary, new words can be formed according to that pattern. A meaning of the suffix -ista is 'person who practices the art or science of....' This suffix allows the derivation of biologista from biologia, physicista from physica, and so on. An Interlingua speaker can freely form saxophonista from saxophone and radiographista from radiographia by following the same pattern.

As noted above, the only limits to free word-building in Interlingua are clarity and usefulness. These concepts are touched upon here:

Any number of words could be formed by stringing roots and affixes together, but some would be more useful than others. For example, the English word rainer means 'a person who rains', but most people would be surprised that it is included in English dictionaries. The corresponding Interlingua word pluviator is unlikely to appear in a dictionary because of its lack of utility. Interlingua, like any traditional language, could build up large numbers of these words, but this would be undesirable.

Gode stressed the principle of clarity in free word-building. As Gode noted, the noun marinero ('mariner') can be formed from the adjective marin, because its meaning is clear. The noun marina meaning 'navy' cannot be formed, because its meaning would not be clear from the adjective and suffix that gave rise to it.

Interlingua has been developed to omit any grammatical feature that is absent from any one primary control language. Thus, Interlingua has no noun–adjective agreement by gender, case, or number (cf. Spanish and Portuguese gatas negras or Italian gatte nere, 'black female cats'), because this is absent from English, and it has no progressive verb tenses (English I am reading), because they are absent from French. Conversely, Interlingua distinguishes singular nouns from plural nouns because all the control languages do.^[35] With respect to the secondary control languages, Interlingua has articles, unlike Russian.

The definite article le is invariable, as in English ("the"). Nouns have no grammatical gender.^[35][40] Plurals are formed by adding -s, or -es after a final consonant.^[35] Personal pronouns take one form for the subject and one for the direct object and reflexive. In the third person, the reflexive is always se.^[35][40] Most adverbs are derived regularly from adjectives by adding -mente, or -amente after a -c. An adverb can be formed from any adjective in this way.^[41]

Verbs take the same form for all persons (io vive, tu vive, illa vive, 'I live', 'you live', 'she lives'). The indicative (pare, 'appear', 'appears') is the same as the imperative (pare! 'appear!'), and there is no subjunctive.^[35] Three common verbs usually take short forms in the present tense: es for 'is', 'am', 'are;' ha for 'has', 'have;' and va for 'go', 'goes'.^[40] A few irregular verb forms are available, but rarely used.^[42]

There are four simple tenses (present, past, future, and conditional), three compound tenses (past, future, and conditional), and the passive voice. The compound structures employ an auxiliary plus the infinitive or the past participle (e.g., Ille ha arrivate, 'He has arrived').^[35] Simple and compound tenses can be combined in various ways to express more complex tenses (e.g., Nos haberea morite, 'We would have died').^[43]

Word order is subject–verb–object, except that a direct object pronoun or reflexive pronoun comes before the verb (io les vide, 'I see them').^[35][40] Adjectives may precede or follow the nouns they modify, but they most often follow it.^[35] The position of adverbs is flexible, though constrained by common sense.^[40]

The grammar of Interlingua has been described as similar to that of the Romance languages, but simplified, primarily under the influence of English.^[35] A 1991 paper argued that Interlingua's grammar was similar to the simple grammars of Japanese and particularly Chinese.^[44]

F. P. Gopsill has written that Interlingua has no irregularities, although Gode's Interlingua Grammar suggests that Interlingua has a small number of irregularities.^[35][34]

One criticism that applies to naturalistic constructed languages in general is that if an educated traveler is willing to learn a naturalistic conlang, they may find it even more useful to learn a natural language outright, such as International English. Planned conlangs at least hold out the promise of "fixing" or standardizing certain irregular aspects of natural languages and providing unique advantages, despite the lack of speakers, but naturalistic conlangs have to compete with the natural languages they are based on. In practice, conferences with international attendance tend to be held in a natural language popular among the attendees rather than an international auxiliary language.

From an essay by Alexander Gode:

Interlingua se ha distacate ab le movimento pro le disveloppamento e le introduction de un lingua universal pro tote le humanitate. Si on non crede que un lingua pro tote le humanitate es possibile, si on non crede que le interlingua va devenir un tal lingua, es totalmente indifferente ab le puncto de vista de interlingua mesme. Le sol facto que importa (ab le puncto de vista del interlingua ipse) es que le interlingua, gratias a su ambition de reflecter le homogeneitate cultural e ergo linguistic del occidente, es capace de render servicios tangibile a iste precise momento del historia del mundo. Il es per su contributiones actual e non per le promissas de su adherentes que le interlingua vole esser judicate.^[45]

Interlingua has detached itself from the movement for the development and introduction of a universal language for all humanity. Whether or not one believes that a language for all humanity is possible, whether or not one believes that Interlingua will become such a language is totally irrelevant from the point of view of Interlingua itself. The only fact that matters (from the point of view of Interlingua itself) is that Interlingua, thanks to its ambition of reflecting the cultural and thus linguistic homogeneity of the West, is capable of rendering tangible services at this precise moment in the history of the world. It is by its present contributions and not by the promises of its adherents that Interlingua wishes to be judged.

As with Esperanto, there have been proposals for a flag of Interlingua;^[46] the proposal by Czech translator Karel Podrazil is recognized by multilingual sites.^[47] It consists of a white four-pointed star extending to the edges of the flag and dividing it into an upper blue and lower red half. The star is symbolic of the four cardinal directions, and the two halves symbolize Romance and non-Romance speakers of Interlingua who understand each other.

Another symbol of Interlingua is the Blue Marble surrounded by twelve stars on a black or blue background, echoing the twelve stars of the Flag of Europe (because the source languages of Interlingua are purely European).

• 
  Unofficial flag often appearing in the Interlingua-speaking community
• 
  Unofficial flag of Interlingua proposed by Karel Podrazil
• 
  Another possible flag of Interlingua

• Falk, Julia S. Women, Language and Linguistics: Three American stories from the first half of the twentieth century. Routledge, London & New York: 1999.
• Gode, Alexander; Blair, Hugh E. (1955) [1951]. Interlingua; a grammar of the international language (Second ed.). New York: Frederick Ungar Publishing. ISBN 0-8044-0186-1. OCLC 147452. Retrieved 2007-03-05.
• International Auxiliary Language Association (1971) [1951]. Alexander Gode (ed.). Interlingua-English; A dictionary of the international language (Second ed.). New York: Frederick Ungar Publishing. ISBN 0-8044-0188-8. OCLC 162319. Archived from the original on 2007-12-27. Retrieved 2010-04-18.
  • Bray, Mary Connell (1971) [1951]. ""Foreword" and "Acknowledgements"". In Alexander Gode (ed.). Interlingua-English; A dictionary of the international language (Second ed.). New York: Frederick Ungar Publishing. ISBN 0-8044-0188-8. OCLC 162319. Archived from the original on 2007-10-17. Retrieved 2010-04-18.
• Gopsill, F. P. (1990). International languages: a matter for Interlingua. Sheffield, England: British Interlingua Society. ISBN 0-9511695-6-4. OCLC 27813762.
• Gopsill, F.P. Le historia antenatal de Interlingua.. (In Interlingua.) Accessed 28 May 2005.
• International Auxiliary Language Association (IALA). General Report. IALA, New York: 1945.
• Pei, Mario. One Language for the World and How To Achieve It. Devin-Adair, New York; 1958.
• Sexton, Brian C.; Wilgenhoff, Karel; and F. Peter Gopsill. Supplementary Interlingua-English Dictionary. British Interlingua Society, Sheffield, 1991
• Union Mundial pro Interlingua (UMI). Interlingua 2001: communication sin frontieras durante 50 annos Archived 2015-04-22 at the Wayback Machine (in Interlingua). Accessed 17 August 2006.

• Official website
• Collection of links to Interlingua resources
• Word Building, in A Grammar of Interlingua by Alexander Gode and Hugh E. Blair, IALA, 1951.
• Formation de parolas in Interlingua (PDF), by Ingvar Stenström, Swedish Society for Interlingua. (In Interlingua)
• Historia de Interlingua