Interlingua/Verbs

Main verb forms
Tense	Ending	-ar verbs	-er verbs	-ir verbs
Infinitive	-r	parlar	vider	audir
Present	–	parla	vide	audi
Past*	-va	parlava	videva	audiva
Future*	-ra	parlara	videra	audira
Conditional*	-rea	parlarea	viderea	audirea
Present participle	-(e)nte	parlante	vidente	audiente
Past participle	-te	parlate	vidite	audite
*For alternative, compound forms, see Compound tenses.

The verb system is a simplified version of the systems found in the Romance languages. There is an imperfective aspect, as in Romance, no perfect as in English, and no continuous aspect, as in English and some Romance languages. Except for esser 'to be', there are no personal inflections, and the indicative also covers the subjunctive and imperative moods. Three common verbs (esse, habe and vade) usually take short forms in the present tense (es, ha and va respectively), and a few irregular verbs are available.

For convenience' sake, this section often uses the term tense to also cover mood and aspect, though this is not strict grammatical terminology.

The table at the right shows the main verb forms, with examples for -ar, -er and -ir verbs (based on parlar 'to speak', vider 'to see', and audir 'to hear').

The simple past, future, and conditional tenses correspond to semantically identical compound tenses (composed of auxiliary verbs plus infinitives or past participles). These in turn furnish patterns for building more-complex tenses such as the future perfect.

Infinitives

Infinitive verbs always end in -ar, -er, or -ir. They cover the functions of both the infinitive and the gerund in English and can be pluralized where it makes sense.

Cognoscer nos es amar nos.   'To know us is to love us.'

Il es difficile determinar su strategia.   'It's hard to figure out his strategy.'

Illes time le venir del locustas.   'They fear the coming of the locusts.'

Le faceres de illa evocava un admiration general.   'Her doings evoked a widespread admiration.'

Infinitives are also used in some compound tenses (see below).

Simple tenses

There are four simple tenses: the present, past, future, and conditional.

• The present tense can be formed from the infinitive by removing the final -r. It covers the simple and continuous present tenses in English. The verbs esser 'to be', haber 'to have', and vader 'to go' normally take the short forms es, ha, and va rather than esse, habe, and vade.

Io ama mangos; io mangia un justo ora.   'I love mangoes; I'm eating one right now.'

Mi auto es vetere e ha multe defectos: naturalmenti illo va mal!   'My car is old and has lots of things wrong with it: of course it runs poorly!'

• The simple past tense can be formed by adding -va to the present tense form. It covers the English simple past and past perfect, along with their continuous equivalents.

Io vos diceva repetitemente: le hospites jam comenciava partir quando la casa se incendiava.   'I've told you again and again: the guests were already starting to leave when the house burst into flames.'

• The simple future can be formed by adding -ra to the present tense form. Future tense forms are stressed on the suffix (retornara 'will return'). It covers the English simple and continuous future tenses.

Nos volara de hic venerdi vespere, e sabbato postmeridie nos prendera le sol al plagia in Santorini.   'We'll fly out Friday evening, and by Saturday afternoon we'll be sunbathing on the beach in Santorini.'

• The simple conditional consists of the present tense form plus -rea. Like the future tense, it is stressed on the suffix (preferea 'would prefer). In function it resembles the English conditional.

Si ille faceva un melior reclamo, ille venderea le duple.   'If he did better advertising, he would sell twice as much.'

Participles

The present participle is effectively the present tense form plus -nte. Verbs in -ir take -iente rather than *-inte (nutrir 'to feed' → nutriente 'feeding'). It functions as an adjective or as the verb in a participial phrase.

un corvo parlante   'a talking crow'

Approximante le station, io sentiva un apprehension terribile.   'Approaching the station, I felt a sense of dread.'

The past participle can be constructed by adding -te to the present tense form, except that -er verbs go to -ite rather than *-ete (eder 'to edit' → edite 'edited'). It is used as an adjective and to form various compound tenses.

un conto ben contate   'a well told story'

Compound tenses

Three compound tenses – the compound past, future, and conditional – are semantically identical with the corresponding simple tenses.

• The compound past tense consists of ha (the present tense of haber 'to have') plus the past participle.

Le imperio ha cadite.   =   Le imperio cadeva.   'The empire fell.'

• The compound future tense is constructed from va (the present tense of vader 'to go') plus the infinitive.

Io va retornar.   =   Io retornara.   'I shall return.'

• The rarely used compound conditional tense uses the auxiliary velle plus the infinitive.

Io velle preferer facer lo sol.   =   Io prefererea facer lo sol.   'I'd prefer to do it alone.'

The fourth basic compound tense is the passive, formed from es (the present tense of esser 'to be') plus the past participle.

Iste salsicias es fabricate per experte salsicieros.   'These sausages are made by expert sausage-makers.'

A wide variety of complex tenses can be created following the above patterns, by replacing ha, va, and es with other forms of haber, vader, and esser. Examples:

• The future perfect, using habera 'will have' plus the past participle

Ante Natal, tu habera finite tu cursos.   'By Christmas you will have finished your courses.'

• The past imperfect, using vadeva 'were going' plus the infinitive

Plus tarde illa vadeva scriber un romance premiate.   'Later she would write a prize-winning novel.'

• The passive-voice past perfect, using habeva essite 'had been' plus the past participle

Nostre planeta habeva essite surveliate durante multe annos.   'Our planet had been watched for many years.'

Other tenses

There are no distinct forms for the imperative and subjunctive moods, except in the case of esser 'to be'. Present-tense forms normally serve both functions. For clarity's sake, a nominative pronoun may be added after the verb.

Face lo ora!   'Do it now!'

Le imperatrice desira que ille attende su mandato.   'The empress desires that he await her command.'

Va tu retro al campo; resta vos alteros hic.   'You, go back to the camp; you others, stay here.'

The infinitive can serve as another, stylistically more impersonal, imperative form.

Cliccar hic.   'Click here.'

A less urgent version of imperative, the cohortative, employs a present-tense verb within a "that" ("que") clause and may be used with the first and third person as well as the second. The alternative vamos 'let's' (or 'let's go') is available for the second-person plural.

Que tu va via!   'I wish you'd go away!'

Que illes mangia le brioche.   'Let them eat cake.'

Que nos resta hic ancora un die.   or   Vamos restar hic ancora un die.   'Let's stay here one more day.'

Sia is the imperative and subjunctive form of esser 'to be'. The regular form esse may also be used.

Sia caute!   'Be careful!'

Sia ille vive o sia ille morte...   'Be he alive or be he dead...'

Que lor vita insimul sia felice!   'May their life together be happy!'

Irregular verbs

The only irregular verb forms employed by most users are es, ha, and va – the shortened present-tense forms of esser 'to be', haber 'to have' and vader 'to go' – plus sia, the imperative/subjunctive of esser.

There are certain collateral forms of esser 'to be': son (present plural), era (past), sera (future), and serea (conditional), instead of es, esseva, essera, and esserea.

• Nos vancouveritas son un banda pittoresc.   =   Nos vancouveritas es una banda pittoresca.   'We Vancouverites are a colourful lot.'

• Le timor era incognoscite.   =   Le timor esseva incognoscite.   'Fear was unknown.'

• Que sera, sera.   =   Que essera, essera.   'What will be, will be.'

• Il serea melior si nos non veniva.   =   Il esserea melior si nos non veniva.   'It would be better if we hadn't come.'

The forms io so 'I am' and nos somos 'we are' also exist but are rarely used.

Double-stem verbs

The Neolatin vocabulary that underlies Interlingua includes a group of verbs whose stems mutate when attached to certain suffixes. For example, agente, agentia, actrice, activista, reagente, reaction are all derivatives of ager 'to act', but some use the primary stem ag-, while others use the secondary stem act-. There are hundreds of such verbs, especially in international scientific vocabulary.

sentir 'to feel' (second stem: sens-) → sentimento, sensor

repeller 'to push away' (second stem: repuls-) → repellente, repulsive

This raises a logical issue. Adding -e to one of these secondary stems produces an adjective that is structurally and semantically equivalent to the past participle of the same verb. Experte, for example, is related to experir 'to experience', which has the past participle experite. Yet, semantically, there is little difference between un experte carpentero 'an expert carpenter' and un experite carpentero 'an experienced carpenter'. Effectively, experte = experite. Furthermore, one can form a word like le experito 'the experienced one' as a quasi-synonym of le experto 'the expert'.

This process can be reversed. That is, can one substitute experte for experite in compound tenses (and other second-stem adjectives for other past participles).

Io ha experte tal cosas antea.   =   Io ha experite tal cosas antea.   'I've experienced such things before.'

Illa ha scripte con una pluma.   =   Illa ha scribite con una pluma.   'She wrote with a quill.'

The original Interlingua grammar (Gode & Blair, 1951) permitted this usage, and illustrated it in one experimental text. A minority of Interlinguists employ the irregular roots, at least occasionally, more often with recognizable forms like scripte (for scribite 'written') than opaque ones like fisse (for findite 'split'). The practice is controversial. Deprecators suggest that they may confuse beginners. Proponents argue that by using the irregular participles, students of Interlingua become more aware of the connections between words like agente and actor, consequentia and consecutive, and so on. A compromise position holds that the irregular forms may be useful in some educational contexts (e.g., when using Interlingua to teach international scientific vocabulary or as an intermediate step in the study of Romance languages), but not in general communication.

A similar issue concerns the present participles of caper 'to grasp, seize', facer 'to do, make', saper 'to know', and all verbs ending in -ciper, -ficer, and -jicer. The regular forms are facente, sapente, etc., but the "preferred forms", according to the original grammar, are faciente, sapiente, etc.

un homine sapiente   =   un homine sapente   'a knowledgeable person'

Recipiente le littera, ille grimassava.   =   Recipente le littera, ille grimassava.   'Receiving the letter, he grimaced.'

Today, most users employ the regular forms in spontaneous usage. Forms like sufficiente are often used as adjectives, under the influence of similar forms in the source languages.