Summary of the introduction

July and , details.

Introduction to the summary of the introduction

After years of research, Interlingua started with the Interlingua-English dictionary (IED) and the Interlingua Grammar (IG). Both were published in English in 1951.

The IED starts with an Introduction which explains how the words of Interlingua were derived from existing languages. People who want to read texts in Interlingua, or even write in the language, do not need to know that. They can use the existing dictionaries, which are rather extensive.

However, it can be interesting to know about the method of extracting words. Sometimes, when words are needed for things that didn’t exist yet in 1951, and which are not present in later additions to the dictionaries, the method can be applied again.

As said, the Introduction to the Interlingua-English dictionary was written in English. There is a translation in Interlingua, and here and here are versions in both languages, side by side. My summary is in English too, like the original. A translation into Interlingua is in progress also available.

The Introduction is in beautiful English sentences. Beautiful and complicated, with many international words. Too complicated to my liking. In the past years several times, in the evening, tired after other work, I tried to read and understand the Introduction. I read those lovely sentences, and most of the time I understood all the words, but no overall meaning got through to my brain. Too difficult, too complex.

But my English reading and comprehension skills are sufficient. After a good night’s sleep I can understand what those phrases express. So that I have done, and now I will try to rewrite what I have read in much simpler terms, focussing on concrete examples.

I don’t cite any text, to avoid interrupting the flow of reading. But there will be page numbers in Roman numerals, that refer to the 1971 2nd edition of the IED. For example: (xli) means page 41. The links are clickable, so anyone who wants to check the summary against the original text by Alexander Gode, can do so.


The makers of the IED wanted to present an international vocabulary (xvii, xviii). The IED is not a grammar, and it is not an English-Interlingua dictionary.

Some say we should use an existing natural language as the universal auxiliary language. That would mean that people who don’t speak the same language, everywhere in the world, could use that language to communicate.

Such languages have existed. It is usually the language of a powerful country, or the language of a culture that has much influence (xix). Late Greek was such a language, and Latin in the Middle Ages. Swahili plays that role in East Africa, and Mandarin Chinese in China (xix). All these languages are natural languages, not planned or constructed languages.

In the modern world, we have the ‘language’ of science and technology. It is not a full language, but consists of international terms and phrases (xx). That makes it the nucleus, the kernel, of a complete language. It contains fragments of the only truly international language we have.

This nucleus, the international vocabulary, is what the people of IALA (International Auxiliary Language Association) have collected, and in 1951 presented in the IED.

Where from?

We are looking for international words, words that occur in many languages. Words can be international because they are known in related languages. For example, English ‘house’, Frisian ‘hûs’, Dutch ‘huis’, German ‘Haus’, and Swedish ‘hus’ look a bit the same, sound similar, and mean the same. They are international, but only within the group of Germanic languages.

The word ‘automobile’, built in France from an element from Greek and one from Latin, has spread to nearly all the languages of the globe.

The word ‘igloo’ is known in almost all languages, although knowledge of Inuktitut, where it comes from, is clearly not wide-spread (xxi, xxii).

Some languages have received a lot of words. An example is English. Some languages have sent a lot of words, examples are Greek, Latin, its daughters the Romance languages, and English. By looking at such languages, we do not need to consider Inuktitut, because the international word ‘igloo’ will come to us anyway, via other languages.

Many technical and scientific words contain Greek and Latin elements, although they are not really Greek of Latin words. A native speaker of Ancient Greek would not know what a telephone is, because the device had not been invented yet, and the word didn’t exist in Greek, although both elements are Greek in origin (xxiii).


A word is international if it is found in three of the four languages Italian, Spanish and/or Portuguese, French and English. In those languages, the words must be similar in form and meaning. German and Russian may be used for extra support, if not enough of the other languages have the word. Spanish and Portuguese are both important languages, but their contribution is often the same, therefore they count as one language only (xxv, xxvi).

Not just the modern words of the modern languages count, but also older words, that may have left their traces. For example, it seems hard to find an international word for ‘to kill’. French has ‘tuer’, Spanish and Portuguese have ‘matar’, Italian has ‘uccidere’. All different. What to do?

The solution is in French ‘occire’, now obsolete or humorous, and in Spanish ‘occiso’, originally the past participle of a now unused verb ‘occidir’. So the Interlingua word is: occider (xxvii).

The words found in the control languages must be of corresponding form, but we need not be too strict about that. For example, Italian ‘amaritudine’ does not correspond perfectly to French ‘amertume’ and Spanish ‘amargor’. There are also the Italian words ‘amarore’ and ‘amarezza’, with different suffixes yet again.

All those words have the same meaning. Despite the different endings, they may be used to derive an international word: ‘amaritude’.

Similar examples: English ‘fanatical’, French ‘fanatique’, Italian ‘fanatico’. Interlingua: fanatic. The meaningless extra suffix of English, ‑al, is not a problem. The same with ‑ious: English ‘voracious’, French ‘vorace’, Spanish ‘voraz’, Interlingua: ‘vorace’.

The word ‘proximity’ exists in English, but there is no ‘proxim’ and no ‘proximous’. Nonetheless, ‘proxime’ is a good Interlingua word, also supported by English.

‘Fiammifero’ is only Italian, not found in other control languages. But it results in the Interlingua word ‘flammifero’ meaning ‘match’, because the elements ‘flamma’ and ‘‑fero’ do have support in other languages (xxvi, xxvii, xxviii, xxix).

Sometimes there aren’t enough examples in the Romance control languages (Italian, French, Spanish/Portuguese) to include the word in the international vocabulary. Then the English word, that is different in form, but has the same origin via Proto-Indo-European, can make the word valid.

Two examples:

When cognateship via Indo-European is involved, the form of the international word is determined by the Romance language words found (here: in the first example from Spanish, Portuguese and Italian; in the second French and Italian), not from the Germanic ones (here: English). So the Interlingua words have f, not b, as their first letter and sound.

Reference: page xxxvii.

What form?

International words must not have the form of an Italian, French, Portuguese, English etc. word. Their form should be international (xxix).

The ‘ie’ in ‘tierra’ is typically Spanish, so that should not appear in the Interlingua word for ‘earth’. The final ‑e of French ‘terre’ is typical of French and of none of the other control languages. So the international word does not end in ‑e. ‘Earth’ in Interlingua is ‘terra’.

The ‑er of French ‘aimer’ is typically French. In Interlingua the word is ‘amar’.

Interlingua has ‘vorace’, not *‘voraciose’ or something like that, because the ‑ious in ‘voracious’ is an English-only whim.

The Latin word ‘causa’ gave rise to two words in Interlingua: causa and cosa. The meanings are different. ‘Causa’ is supported by Spanish and Portugese ‘causa’, and French and English ‘cause’. ‘Cosa’ finds it base in Italian and Spanish ‘cosa’, Portuguese ‘cousa’ (now ‘coisa’), and French ‘chose’ (xxx).

Terminations ‑al(e) and ‑il(e)

Latin words in ‑alis had a case form in ‑ale, which become the basis for the words in Romance control languages. However, it survives as such only in Italian, the other ones have just ‑al. Therefore Interlingua has ‑al too (xxx, xxxi).

About Latin words in ‑ilis (xxxi):

Latin Latin
(oblique case)
Italian Spanish / Portu­guese French English Inter­lingua
agilis agile agile ágil agile agile agile
fossilis fossile fossile fósil / fóssil fossile fossil fossile
cīvīlis cīvīle civile civil / cível, civil civil civil civil
mōbilis mōbile automobile automóvil / automóvel automobile automobile automobile
infantilis infantile infantile infantil infantile infantile infantil
ōrdō ōrdine ordine orden / ordem ordre order ordine
asinīnus asinīnō asinino asinino asinin asinine asinin
arbor arbore albero árbor / árvore arbre arbore
professor professōre professore profesor / professor professeur professor professor
Latin Latin
(oblique case)
Italian Spanish / Portu­guese French English Inter­lingua

Some comments on what we can see in the above table:

The left column is the nominative of Classical Latin. However, most words in Romance languages have developed from the collapse into one, of non-nominative cases, in Vulgar Latin, which together are called oblique case. Those forms are in the second column of the table (xxxi).

In English ‘agile’ and ‘fossil’ have different endings, but this is not seen the other control languages. Therefore those words are ‘agile’ and ‘fossile’ in Interlingua, each with the same ending ‑ile.

When comparing the forms in various languages, of what has become ‘civil’ and ‘agile’ in Interlingua, we see a stress pattern: when the ending is ‑il, the stress falls on it (e.g civíl); when it is ‑ile, the stress falls on the syllable before the ending (e.g. ágile). The same pattern exists with the letters ‘n’ and ‘r’ instead of ‘l’: compare ‘asinin’ (stressed asinín) and ordine (órdine); and professor (professór) but arbore (árbore).

This is the ‘lenere’ pronunciation rule (xxxi, liii).

Termination of infinitives

Infinitives in Interlingua end in ‑ar, ‑er or ‑ir, because only Italian has ‑are, ‑ere and ‑ire (xxxi) (*).

Most verbs that have ‑er in Interlingua had ‑ēre in Latin. The long ē was stressed. However, some Latin verbs had a short 'e' there (ĕ), and the stress fell on the syllable before that.

The note in the bottom of the page of Paragraph 148 of the Interlingua Grammar describes a collateral variant of Interlingua, in which those two types of verbs would be distinguished. Latin verbs in ‑ĕre would have ‑ere in Interlingua, with the stress before that suffix. Examples: áddere, dícere and pérdere. Latin verbs in ‑ēre end in ‑er in this collateral Interlingua, as in the standard form of the language. The suffix is stressed, for example ‘temér’ and ‘facér’ (xxxi). (The accent marks on vowels are only used here for clarity, but are not used in the normal spelling of Interlingua.)

In standard Interlingua, Latin verbs in both ‑ĕre and ‑ēre have ‑er in Interlingua, which is the stressed syllable of those words. Examples: adder, dicer and perder, pronounced addér, dicér and perdér.

There is a connection between this difference that existed in Latin, and the presence of regular and irregular stems from which other words can be derived. More info is in Appendix I of the Interlingua Grammar.

Termination of adjectives

In Romance languages French, Italian, Spanish and Portuguese, many adjectives have different forms, depending on whether the noun they belong to is feminine or masculine. For example in Spanish you can say Santa María, but Santo Domingo.

Other adjectives however have only one form. In Portuguese, you can say “O Brasil é um grande país. São Paulo é uma grande cidade.” The adjective is “grande” in both cases, even though “cidade” is a feminine noun and “país” is a masculine noun.

In Interlingua too, this adjective is ‘grande’. If Interlingua followed the grammars of Romance languages, it would have forms ‘sancta’ and 'sancto’. But it does not: Interlingua follows English in this respect. Therefore the adjective is always simply ‘sancte’ (xxxii).

It would be possible to use the international vocabulary with different grammars, which do distinguish between feminine and masculine words. This has been tried. (xxxii).

Related words

The Interlingua word for ‘foot’ is ‘pede’ with a ‘d’, although the Latin word was ‘pes’ with the letter ‘s’. The reason is that words in Romance languages usually do not come from the Latin word form of the nominative case, which is listed in dictionaries. French ‘pied’ and Italian ‘piede’ are from Latin ‘pedem’, the accusative case.

An extra advantage of using this as the basis of the Interlingua word too, is that you see the relation with other words more easily. Examples are the Interlingua words pedal, pedestallo, pedon, pedestre, which all have that letter ‘d’ (xxxii, xxxiii).

Another case where you see related words is: temporal, temporari, temporanee, temporisar, temporisation. The words for ‘time’ is ‘tempore’, to keep that link, even though in the source languages we see Italian and Portuguese tempo, and Spanish tiempo.

There is also a word ’tempo’ in Interlingua, a Italian musical term borrowed by many languages. It means the speed of music, and by extension also the speed of walking, etc. (xxxiii, xxxiii).

‘Heart’ is Interlingua is ‘corde’, showing the relation with cordial, cordialitate, cordifolie, cordiforme, cordipetale. The source languages however do not have that ‘d’ in the base word: Italian cuore, French cœur, Portuguese cor, coração, Spanish corazón (xxxiii). (‘Corage’ however does not have the d in Interlingua; it is from a Latin derivation which also did not have it.)

Sometimes the same Latin word leads to two different word families or derivational series. This can happen when both natural language evolution, and later borrowing are at play. Source languages are then said to have doublets (xxxiv).

Latin Italian Spanish Portu­guese French English Inter­lingua
causa cosa cosa cousa, coisa chose (thing) cosa
causa causa causa cause cause causa

Other cases, with more complicated causes, are:

Latin Italian Spanish Portu­guese French English Inter­lingua
(Vulgar: pēsāre)
pesare pesar pesar peser (to weigh) pesar
pēnsāre pensare pensar pensar penser (to think) pensar

Ref. xxxv. Yet another example:

Latin Italian Spanish Portu­guese French English Inter­lingua
prehensio, prensio prigione prisión prisão prison prison prision
prensione prensión preensão préhension prehension prehension, prension

(Ref. xxxv).

Non-Latin examples

The words which in Interlingua appear as therapeutic and therapia share an origin, via New Latin, in the Greek verb θεραπεύω (therapeúō). However the two were not derived from each other. Therefore in the Interlingua-English dictionary, they are two separate words, and the form of one is not influenced by the form of the other (xxxvi, xxxvi).

Sometimes words found in Romance control languages have their origins in Germanic languages. Example: Italian aringa, Spanish and Portuguese arenque, French hareng. The English form ‘herring’ and the German ‘Hering’ do help make the word international, but can be ignored when determining the form of the word in Interlingua, as was the case (although in a somewhat different situation) for beech and brother. The Interlingua word is haringo (xxxvii) (*).

English carafe, Italian caraffa, French carafe came into those languages from Spanish/Portuguese garrafa, which in turn have it from an Arabic word gharrâf. In Interlingua the word is carrafa because the initial g- is overruled by the c- in the other languages (xxxviii) (*).


Not only etymology and form are important, also meaning (xxxix, xl, xli, xli).

Active word building

Once a word is found to be part in the international vocabulary, other words can be derived from it. Here is a list of prefixes and suffixes, and the details can be found in the Interlingua Grammar.

Dates of writing: 26 and 29–31 July, 1–2, 8–10, 15, 17 and 18 August 2020