A Grammar of Interlingua

Alexander Gode & Hugh Blair | IALA 1951

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Parts of Speech



The verb has an infinitive and two participles (past and present); it has an imperative; and it has four simple tenses (present, past, future, conditional). It uses auxiliaries to form a full set of compound tenses as well as the passive. It has no personal inflection and no subjunctive (but see §111 below). There is no auxiliary corresponding to English 'to do' for use in emphatic and interrogative constructions. There are no crystallized progressive forms (but see §94).


The INFINITIVE ends always in -r with one of the vowels a, e, i preceding (For a collateral verbal system with a further distinction of infinitives in -r and -re after -e-, see below §148 Note; also the note on participles, §97.)

crear 'to create'
rider 'to see'
audir 'to hear'


On the formation of infinitives as well as of derivatives from them, see §140, §145-§150, §153-§154, §155, §157.


The infinitive can be used as a noun and as such it corresponds to the English gerund.

le venir del estate
'the coming of summer'

Vider es creder
'Seeing is believing'

le susurrar del motor
'the droning of the motor'

Iste viagiar de un pais al altere es fatigante
'This traveling from one country to another is fatiguing'

le ir e venir del clientes...
'the coming and going of customers'

Le faceres del formicas es interessante a observar
'The doings of ants are interesting to watch'

Note: As the equivalent of the English noun or quasi-noun in '-ing', the infinitive occurs with all sorts of prepositions in constructions corresponding to the English examples 'without going, by doing, before opening, etc.' This also covers the type 'for sewing' as in 'machine for sewing,' i.e., 'sewing machine,' and finally the pattern 'of doing' as in 'capable of doing' and 'we think of doing. ...'

Illes le condemnava sin audir su defensa
'They condemned him without listening to his defense'

Per rumper le osso on potera forsan rectificar su gamba
'By breaking the bone one may perhaps be able to straighten his leg'

Post haber passate le suburbios on pote avantiar plus rapidemente
'After having passed the suburbs one can get ahead faster'

Io vole ben humiliar me ante ille usque corriger su grammatica sed non usque pagar su debitas
'I am willing to humiliate myself before him to (the point of) correcting his grammar but not to (the point of) paying his debts'

Le sala a attender deberea esser equipate de un machina a scriber
'The waiting room ought to be equipped with a typewriter'

Comencia tu studios per arder omne libros
'Begin your studies by burning all books'

Illa es capace de perder le traino
'She is capable of missing the train'

Nos pensa ir al theatro
'We are thinking of going to the theater'

On the lack of an equivalent of the English 'of' in the last example, see §87 below.


Detached from the sentence the infinitive is not preceded by a preposition corresponding to the English 'to' as in 'to go,' etc. This 'to' is a peculiarly English phenomenon and must not be confused with the use of 'to' before an infinitive within a complete sentence. Here 'to' has a grammatical function and is required or omitted in accordance with specific grammatical rules which make us say 'I need to eat' with 'to' and 'I need not eat' without 'to.' Within a sentence the equivalent of English 'to' before the infinitive is de or a or pro or nothing as differentiated below.


The preposition a is used when the infinitive seems to represent a goal either after an adjective or a verbal construction.

Nos aspira a realisar nostre ideales
'We strive to realize our ideals'

Iste porta non es facile a aperir
'This door is not easy to open'


The preposition pro is used when the infinitive seems to represent a purpose as in an English construction with 'in order to.'

llle venira pro reparar le fenestra
'He came (in order) to repair the window'

Io mangia pro viver, sed quando nos ha globos de patata io vive pro mangiar
'I eat to live but when we have potato dumplings I live to eat'


A preposition need not be used when the infinitive can be construed as a noun or as occupying the place of a noun. (a) In an example like, 'It is difficult to walk in the sand,' the infinitive is the logical subject and hence the equivalent of a noun; the statement is identical with 'Walking in the sand is difficult.' Here the infinitive appears without a preceding preposition: Il es difficile vader in le arena or Vader in le arena es difficile. See §83 above. (b) Whenever a transitive verb is followed by a dependent infinitive as in 'I plan to go to the country,' the idea it represents can be expressed more or less smoothly by a noun, as in 'I plan a trip to the country' Io plana vader al campania. Hence after a transitive verb the dependent infinitive is not introduced by a preposition.

In van io ha tentate convincer le
'In vain have I tried to convince him'

Il es facile rider con le ridentes e difficile plorar con le plorantes
'It is easy to laugh with the laughing and hard to weep with the weeping'

Il es un grande privilegio esser inter vos iste vespere
'It is a great privilege to be with you tonight'

Nos intende ameliorar nostre methodos de agricultura
'We intend to improve our agricultural methods'

Ille diceva que su soror sperava revider nos
'He said that his sister hoped to see us again'

Illa time esser sol con le patiente
'She is afraid of being alone with the patient'


A preposition before the infinitive cannot be used (a) after constructions with voler, poter, deber, soler and (b) after constructions with lassar, facer, also vider, audir and other verbs of sense perception when they have an object which is at the same time the subject of the following infinitive, as in 'I see him come.'

Io volerea dormir sed illa debe dansar
'I would (want to) sleep but she must dance'

Illa crede que illa pote cantar
'She thinks that she can sing'

Le matre faceva le doctor venir or Le matre faceva venir le doctor
'The mother had (made) the doctor come'

Io senti le nausea montar
'I feel the nausea rise'

Io audi le venir or Io le audi venir
'I hear him come (coming)'

Note: In the statement, Io face le studente acceptar mi consilio 'I make the student accept my advice,' the nouns can naturally be replaced by pronouns to yield the simpler form, Io le face acceptar lo 'I make him accept it.' Logically the latter statement ought to be a basis for the two assertions, 'I make him accept' (i.e., I force him to accept) and 'I make accept it' (i.e., I force people in general to accept it). Actually the forms Io le face acceptar and Io face acceptar lo are correct, though the second would not appear in English as 'I make accept it' but as 'I have it accepted' or 'I cause it to be accepted.' Similar examples are:

Illa me faceva vender le can
'She made me sell the dog'

Illa faceva vender le can
'She had the dog sold'

Io videva le infantes occider le ave
'I saw the children kill the bird'

Io les videva occider lo
'I saw them kill it'

Io videva occider lo
'I saw it being killed'


The neutral preposition used with the infinitive is de.

Io es felice de revider vos
'I am happy to see you again'

Le necessitate de ganiar plus es clar
'The need to earn more is clear'

Ille se effortia de mitter le motor in motion
'He tries hard to start the motor'


Note: English constructions of the type, 'I want him to come' can only be rendered as 'I want that he come.' Io vole que ille veni. English constructions such as 'I had the pleasure of seeing her' are always rendered as 'I had the pleasure to see her' Io habeva le placer de vider la.


THE INFINITIVE IS USED to express general orders, prohibitions, etc.

Non fumar! 'Don't smoke!, No smoking!'
Non sputar super le solo! 'Don't spit on the floor!'
Tener se al dextra! 'Keep to the right!'


The infinitive is used after interrogative particles in accordance with the English model, 'I don't know what to do.'

Io non sape que facer

Il es difficile decider se ubi vader
'It is difficult to decide where to go'

Que creder nunc?
'What are we to believe now?'

Nos non sapeva qual pisce prender primo
'We did not know what fish to catch first'


The PRESENT PARTICIPLE ends in -nte which is added to the infinitive less its final -r, with the proviso that a preceding -i- changes to -ie-.

crear: creante 'to create: creating'
vider: vidente 'to see: seeing'
audir: audiente 'to hear: hearing'

Note: The following present participles have -iente as the preferred form although the corresponding infinitives end in -er: capiente and all compounds of -cipiente (incipiente, etc.), faciente and all compounds in -ficiente (deficiente, etc.), all compounds of -jiciente (injiciente, etc.), sapiente, and all compounds of -spiciente (inspiciente, etc.). Since the suffix -antia and its variants -entia, -ientia (see §152) are derived from present-participle forms, their connection with verbs runs parallel to the formation of present participles. Every verb with a present participle in -iente yields a noun in -ientia, etc.


The present participle is an adjective and as such shares all the characteristics of other adjectives. See §32-§39, §41 above and §152 below. Note: The present participle has no function in the verbal paradigm, for there is no crystallized progressive corresponding to English 'I am buying, hoping, etc.' But phrases like 'A dead dog cannot be living' may of course be translated literally in so far as they make sense.

Un can morte non pote esser vivente

Le climate de Alaska va deveniente plus benigne
'The climate of Alaska keeps (or goes on or is) getting milder'

Minnehaha significa "aqua ridente"
'Minnehaha means "laughing water" '

Transversante le oceano, io habeva un placente aventura
'Crossing the ocean I had a pleasant (pleasing) adventure'

Duo passantes videva le accidente
'Two passers-by (passing ones) saw the accident'

Essente surveliate per le policia, ille non osava mover se
'Being watched by the police, he did not dare to move'


The PAST PARTICIPLE ends in -te which is added to the infinitive less its final -r, with the proviso that a preceding -e- changes to -i-.

crear: create 'to create: created'
vider: vidite 'to see: seen'
audir: audite 'to hear: heard'

Note: Past participles are stressed regularly on the vowel before the last consonant. On a collateral stress system, see footnote to §148 below.


As in English the past participle is used in past compound tenses and in the passive. See §105-§106, §112-§113 below. It is also an adjective and as such shares all the characteristics of other adjectives. Finally it occurs as an absolute participle.

Le pluvia impellite per le vento entra trans le fenestra rumpite
'The rain driven by the wind comes in through the broken window'

Io es fatigate
'I am tired (fatigued)'

Le inviata de Valhalla clama le animas del occiditos
'The envoy of Valhalla calls the souls of the slain'

Impellite per le vento, le pluvia entra in le fenestra


Note: There are considerable numbers of verbal adjectives of the type fisse 'split,' docte 'learned,' benedicte 'blessed,' etc. belonging to the verbs finder, docer, benedicer, etc. Their meaning is identical with that of the normal past participles findite, docite, benedicite, etc. in adjectival use. Verbal adjectives of this type may be made to serve as past participles in all functions inclusive of that of forming past compound tenses. The rule covering this point is as follows: Every verb which has a special contracted ( = irregular) deriving stem listed in the Dictionary can form a collateral past participle by adding the ending -e to that contracted stem. See also §152, last unit.

Ille es absorbite in su labor or Ille es absorpte in su labor
'He is absorbed in his work'

Ille ha assumite le nomine de su femina or Ille ha assumpte le nomine de su femina
'He has assumed the name of his wife'

In le campania on non se senti subjicite al haste del vita moderne or In le campania on non se senti subjecte al haste del vita moderne
'In the country one does not feel subjected to the hurry of modern life'


The TENSE FORMS have no personal inflection and require generally an expressed subject.


The PRESENT TENSE is formed from the infinitive by dropping the final -r. It is stressed in accordance with the rules given in §10.

io, tu, etc. crea, vide, audi
'I, you, etc. create, see, listen (hear)'


The present tense functions naturally as the "UNIVERSAL PRESENT." It extends more freely into the future than is possible in English, especially when the construction contains an unambiguous adverb of time.

Deo ama le homines
'God loves men'

Io non sape lo que es le nomine de iste animal
'I don't know what the name of this animal is'

Iste vespere io recipe mi canetto
'Tonight I am going to get my puppy'


The verbs haber 'to have', esser 'to be', and vader 'to go' have a simplified present-tense form which consists of the fist syllable of the infinitive: ha, es, va.

Proque io ha un terribile mal de capite il es necessari que io va al doctor
'Because I have a terrible headache it is necessary that I go to the doctor'

In the case of esser, a distinct optional plural form son is available.


The PAST TENSE is formed from the infinitive by dropping the final -r and adding the tense ending -va.

io, tu, etc. creava, videva, audiva
'I, you, etc. created, saw, heard (listened)'


The functions of the past tense are the same as in English. Note especially its use in constructions of the type, 'If he was (were) here, I might feel better.'

Heri nos voleva vider le Mercator de Venetia sed nos non poteva obtener billetes e tunc nos videva le Princessa del Czardas. Si vos cognosceva iste operetta vos comprenderea que io prefere Kalman a Shakespeare.
'Yesterday we wanted to see the Merchant of Venice but we couldn't get tickets and so we saw the Czardas Princess. If you knew this operetta you would understand that I prefer Kalman to Shakespeare.'


For esser 'to be' an optional irregular past era 'was, were' is available.


The COMPOUND TENSES OF THE PAST (perfect and pluperfect) are formed as in English by means of the present and past of an auxiliary verb (haber 'to have) and the past participle.

io, tu, etc. ha create, vidite, audite
'I, you, etc. have created, seen, heard'

io, tu, etc. habeva create, vidite, audite
'I, you, etc. had created, seen, heard (listened)


The functions of the past compound tenses cover all functions of the corresponding English forms. The perfect is not as restricted as is English and is synonymous with the simple past.

Su Majestate ha perdite su capite
'His Majesty has lost his head'

Ludovico Dece-Sex ha perdite su capite
'Louis XVI lost his head'


The FUTURE is formed from the infinitive by adding the stressed ending -a, not distinguished by an accent mark.

io, tu, etc. creara, videra, audira
'I, you, etc. will create, see, hear (listen)'

The CONDITIONAL is formed from the infinitive by adding the ending -ea with stress on the -e-, not distinguished by an accent mark.

io, tu, etc. crearea, viderea, audirea
'I, you, etc. would create, see, hear (listen)'


The functions of the future and conditional do not differ from English usage.

Si ille attende assatis longe, ille habera un barba
'If he waits long enough, he will have a beard'

Si illa habeva quatro rotas, illa esserea un omnibus
'If she had four wheels, she would be an omnibus'

Si io esseva un avetto, io volarea a te
'If I were a little bird, I would fly to you'

Note: Both future and conditional have collateral compound forms consisting of the infinitive with the auxiliaries va and velle respectively.

Si ille attende assatis longe, ille va haber un barba
Si illa habeva quatro rotas, illa velle esser un omnibus
Si io esseva un avetto, io velle volar a te


More complex verbal constructions - whether one wishes to call them tenses or not - can freely be formed by means of the material discussed above.

Nos haberea potite venir
'We would have been able to come'

Ille habera finite scriber
'He will have finished writing'


The IMPERATIVE is identical with the present but as a rule it uses no pronouns.

Ama tu vicino como te mesme!
'Love thy neighbor as thyself!'

Aperi le porta!
'Open the door!'

Reguarda hic!
'Look here!'

As in English the pronoun occurs occasionally with the imperative.

Face tu lo que io commanda
'Do you what I order (you to do)'


The functions of the imperative can of course be taken over by an emphatic present tense.

Tu veni hic immediatemente!
'You come here right away!'

For the use of the infinitive with imperative value, see §91 above. The elliptic construction with que... '(I wish) that...' is possible with all persons and serves in particular to express the imperative of the first person plural.

Que ille veni!
'Let him come!, May he come!'

Que nos parti!
'Let's go!'

The dictionary word sia 'be (it)' may be construed as a conjunction or as an exceptional subjunctive of esser. Taken in the latter sense, it enters into constructions of imperative value.

Io ama lilios del valles, sia in le campo, sia in un vaso
'I love lilies of the valley, be it in the open, be it in a vase'

Le juvene maritos sia felice!
'(May) The young couple be happy!'

Sia gentil e face me ille favor
'Be nice and do me that favor'


The PASSIVE auxiliary is esser 'to be.' The tense forms of this auxiliary are fully covered by the foregoing discussion of the verbal conjugation. The following summary of them may be found convenient.

io etc. es
'I am,' etc.
io essera or io va esser
'I will be'
io esseva or io era
'I was'
io esserea or io velle esser
'I would be'
io ha essite
'I have been'
io habera essite or io va haber essite
'I will have been'
io habeva essite
'I had been'
io haberea essite or io velle haber essite
'I would have been'

The full passive forms consist of the auxiliary with a following past participle.

Ille es surveliate per le policia 'He is (being) watched by the police'
Ille esseva surveliate per le policia
Ille ha essite surveliate per le policia
Ille habeva essite surveliate per le policia
Ille essera surveliate per le policia
Ille va esser surveliate per le policia
Ille esserea surveliate per le policia
Ille velle esser surveliate per le policia
Ille habera essite surveliate per le policia
Ille va haber essite surveliate per le policia
Ille haberea essite surveliate per le policia
Ille velle haber essite surveliate per le policia


The passive infinitives and participles are similarly composed of the infinitive and participles of the auxiliary with the past participle of the main verb following.

esser surveliate 'to be watched'
essente surveliate 'being watched'
essite surveliate 'been watched'

Note that the passive as such cannot be distinguished from a form of esser 'to be' with a participial adjective. Io es maritate may mean 'I am being married' and 'I am married.'


The functions of the passive are the same as in English. Note, however, the use of the reflexive in lieu of an English passive. See §68 above. Furthermore an English passive may often be rendered by an impersonal construction with on 'one,' as in On non nos ama hic 'We are not liked around here (One does not like us here).'



Infinitive crear
to create
to see
to hear
Present Participle creante
Past Participle create
Imperative crea!
Active Present io crea
io vide
io audi
I create
I see
I hear
Imperfect io creava
io videva
io audiva
I created
I saw
I heard
Present perfect io ha create
io ha vidite
io ha audite
I have created
I have seen
I have heard
Past perfect io habeva create
io habeva vidite
io habeva audite
I had created
I had seen
I had heard
Future io creara
io videra
io audira
I will create
I will see
I will hear
Future perfect io habera create
io habera vidite
io habera audite
I will have created
I will have seen
I will have heard
Conditional io crearea
io viderea
io audirea
I would create
I would see
I would hear
Conditional perfect io haberea create
io haberea vidite
io haberea audite
I would have created
I would have seen
I would have heard
Passive Present io es create
io es vidite
io es audite
I am created
I am seen
I am heard
Present perfect io ha essite create
io ha essite vidite
io ha essite audite
I have been created
I have been seen
I have been heard
Imperfect io esseva create
io esseva vidite
io esseva audite
I was created
I was seen
I was heard
Past perfect io habeva essite create
io habeva essite vidite
io habeva essite audite
I have been created
I have been seen
i have been heard
Future io essera create
io essera vidite
io essera audite
I will be created
I will be seen
I will be heard
Future perfect io habera essite create
io habera essite vidite
io habera essite audite
I will have been created
I will have been seen
I will have been heard
Conditional io esserea create
io esserea vidite
io esserea audite
I would be created
I would be seen
I would be heard
Conditional perfect io haberea essite create
io haberea essite vidite
io haberea essite audite
I would have been created
I would have been seen
I would have been heard


The normal QUESTION is represented by the English type 'Has he come?' There is no interrogative auxiliary and the English type 'Does he come?' cannot be used.

Ha ille venite?

Veni ille?

Desira vos salsicias con o sin allio?
'Do you want sausages with or without garlic?'

Transversava le rege svede le Mar Baltic o non?
'Did the Swedish king cross the Baltic or didn't he?'

When the question word is the subject, it is not preceded by the verb.

Qui es ille homine con le barba rubie?
'Who is that man with the red beard?'

Que batte a mi fenestra?
'What knocks at my window?'

Que ha tu facite con tu moneta?
'What have you done with your money?'

Quando arriva le traino?
'When does the train come in?'

Ubi es tu melior medietate?
'Where is your better half?'

As in English every normal statement can be turned into a question by intonation and the use of a question mark.

'The price of that stuff was three dollars?'
Le precio de ille cosalia esseva tres dollares?

'You mean to tell me that you did not do it?'
Vos vole dicer me que vos non lo faceva?

The interrogative particle an, which has no equivalent in English, can be used to change any statement into a question. It always occurs at the beginning of the sentence.

An le precio de illo esseva tres dollars?

An vos vole dicer me que vos non lo ha facite?

An vos e vostre amica es reconciliate?
'So you and your friend have made up?'

Note: A collateral form of the interrogative particle is esque; the two forms, an and esque, should not be used in the same text.


The SEQUENCE OF TENSES may be treated in accordance with English usage.

(Ille diceva: "Io es fatigate." 'He said: "I am tired." ')
Ille diceva que ille esseva fatigate 'He said that he was tired'

Deviations from this usage are permissible when suggested by logical considerations.

Io non crede que un decimetro de lana pesa tanto como un decimetro de ferro.
- Nemo diceva que tu debeva creder tal nonsenso or Nemo diceva que tu debe creder tal nonsenso
'I do not believe that a decimeter of wool weighs as much as a decimeter of iron.
- Nobody said that you had (have) to believe such nonsense.'

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