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A Grammar of Interlingua

Alexander Gode & Hugh Blair IALA 1951

Parts of Speech




0 zero
1 un 10 dece
2 duo 20 vinti
3 tres 30 trenta
4 quatro 40 quaranta
5 cinque 50 cinquanta
6 sex 60 sexanta
7 septe 70 septanta
8 octo 80 octanta
9 nove 90 novanta

Note: From cinquanta on the tens are regularly derived from the ones by means of the suffix -anta.

100 cento
1,000 mille
1,000,000 million
1,000,000,000 milliardo
1,000,000,000,000 billion
1,000,000,000,000,000 billiardo
1,000,000,000,000,000,000 trillion
1,000,000,000,000,000,000,000 trilliardo
1,000,000,000,000,000,000,000,000 quatrillion
1,000,000,000,000,000,000,000,000,000 quatrilliardo
1,000,000,000,000,000,000,000,000,000,000 quintillion
1,000,000,000,000,000,000,000,000,000,000,000 quintilliardo

Note: From 1,000,0005 on, the higher powers of a million are formed regularly by means of the suffix -illion added to the stem of the multiplicative corresponding to the exponent. For the forms of the multiplicatives, see below §127. The numeral representing a thousand times any power of one million is formed by replacing the final -ion by the suffix -iardo.

All other cardinals are formed by addition or multiplication.


The principle of addition is used to combine tens with ones; hundreds with tens and ones; thousands with hundreds, tens, and ones; millions with thousands, hundreds, tens, and ones, etc. The items to be added are juxtaposed, the bigger one preceding. Example: 1,120 mille cento vinti. Below a hundred the juxtaposed items are connected by a hyphen. Examples: 72 septanta-duo; 11 dece-un; 12 dece-duo. The use of e 'and' between the items to be added is always possible and always dispensable. In sums below a hundred it replaces the hyphen. Examples: mille cento e vinti; septanta e duo.


The principle of multiplication is used to express multiples of cento, mille, and all higher powers of mille, as million, milliardo, etc. The multiplier is an adjective which always precedes the multiplicand. The multiplicand is a noun which takes a normal plural ending. Examples: 3,000,000 tres milliones; 200 duo centos.

Note: Before cento and mille the multiplier un may be omitted. All the higher powers of 1,000 - as million, milliardo, billion, etc. - introduce the object they count by the preposition de. Example: un billion de dollares.


There is no difference in form between cardinal numerals used as adjectives and pronouns except for un 'one,' whose pronominal forms coincide with those of the indefinite article (see §21 above).


Examples of cardinal numerals:

13 dece-tres
8.347 octo milles tres centos quaranta-septe
10.987.654.321 dece milliardos nove centos octanta-septe milliones sex centos cinquanta-quatro milles tres centos vinti-un

Le mille-pedes ha perdite quatro centos novanta-nove pedes; illo totevia ha cinque centos un
'The millepede has lost four hundred and ninety-nine feet; it still has five hundred and one.'

In bon tempores ille emplea plus que cento filanderas in su filanda; nunc ille ha travalio pro exactemente quaranta-una
'In good times he employs more than a hundred girls in his spinning mill; now he has work for exactly forty-one.'


DECIMALS are written and read with a comma instead of a period:

34.798 (thirty-four point seven nine eight)
34,798 (trenta-quatro comma septe nove octo).

Note: The English custom of setting off long numbers by a comma (e.g., 1,234,567,890) would conflict with the decimal comma. In its stead the Interlingua uses a period (e.g. 1.234.567.890).


Model readings of arithmetical rules:

14 + 3,4 = 17,4 (dece-quatro plus tres comma quatro es dece-septe comma quatro)

20 - 102 = -82 (vinti minus cento duo es minus octanta duo)

20 x 17 = 340 (vinti vices dece-septe es tres centos quaranta)

100 ÷ 3 = 33,3333 (cento dividite per tres es trenta-tres comma tres tres tres tres)


The ORDINAL NUMERALS are adjectives sharing all characteristics of other adjectives in regard to pronominal and substantivized use. The basic ordinals are:

1st prime
2nd secunde
3rd tertie
4th quarte
5th quinte
6th sexte
7th septime
8th octave
9th none
10th decime
last ultime

All other simple ordinals are derived from the corresponding cardinals by the suffix -esime:

20th vintesime
30th trentesime
100th centesime
1,000th millesime
1,000,000th millionesime
1,000,000,000th milliardesime

In compound numerals only the last element is given the form of an ordinal:

11th dece-prime
102nd cento secunde
99th novanta-none
300th tres centesime

'The two hundred fiftieth anniversary'
le duo cento cinquantesime anniversario

'This is my third (presumably: cocktail)'
Isto es mi tertie

In Arabic numerals the ordinals are expressed as follows:

1me, 2nde, 3tie, 4te, 5te, 6te, 7me, 8ve, 9ne, 10me, 20me, 100me


The FRACTIONAL adjective 'half' is medie, the corresponding noun medietate. Joined to the following noun, medie- has the value of English 'mid-.'

un medie hora
'half an hour (a half hour)'
duo medie horas
'two half hours';
le duo medietates
'the two halves'
duo e medie horas, duo horas e medie
two and a half hours, two hours and a half
le medietate del membros
'half the members'
le medie membros
'the half members (opposed to 'full members')'

All other fractional numerals are formed after the following patterns: Phrases like 'a fourth part, two fifth parts, one sixth part, etc.' are expressed as in English by means of simple ordinals: un quarte parte, duo quinte partes, un sexte parte, etc. In most cases fractions are expressed in phrases differing from the samples given by the absence of 'part' (parte). Instead the ordinals are made into nouns. Note that the model 'three quarter mile' must always be rendered as 'three fourths of a mile.'

Tres quartos plus tres octavos es un e un octavo
'Three fourths and three eighths is one and one eighth'

Un medie hora e un quarto de hora es tres quartos de hora
'Half an hour and a quarter hour is three quarter hours'

In mixed numbers which are used as numeral adjectives, the fraction may follow the noun.

un pan e tres quartos
'one and three quarter loaves of bread'

duo milliones e tres quintos de prisioneros
'two and three fifths million prisoners'


The MULTIPLICATIVE numeral adjectives are:

simple or simplice
duple or duplice
triple or triplice


MULTIPLICATIVE COMPOUNDS ('half-yearly,' 'threedecker,' etc.) can be formed freely after the following models in which the compounding forms of the numerals function as prefixes. Note that compounds of this category may involve simultaneous derivation (after the model of English 'three-cornered' which is not simply a compound of 'three' and 'cornered' but a compounded derivative of 'three' and 'corner' with the suffix '-ed'). Cf. also §155, §163-§164 below. The compounding methods illustrated may be applied equally and indifferently - within the limits of practical needs for new formations - to nouns, adjectives, and verbs.


uni- plus trinitate yields unitrinitate 'unitrinity'
uni- plus corno 'horn' plus adj. ending yields unicorne 'one-horned'
uni- plus latere 'side' plus -al yields unilateral

new formations:

uni- plus monte 'mountain' yields unimonte 'single mountain'
uni- plus anulo 'ring' plus -ate yields unianulate 'one-ring'

Note: The form mono-, before vowels mon-, is used as a synonym of uni- especially in technical terms.

One and one half:

sesqui- plus plano yields sesquiplano 'biplane with short underplane'
sesqui- plus pede 'foot' plus -al yields sesquipedal 'sesquipedalian'

new formations:

sesqui- plus torno 'turn' yields sesquitorno 'one-and-a-half turn'
sesqui- plus uncia 'inch' plus -al yields sesquiuncial 'one and a half inches (in length)'


bi- plus cyclo yields bicyclo 'bicycle'
bi- plus metallo plus -ismo yields bimetallismo 'bimetallism'
bi- plus furcar yields bifurcar 'to bifurcate'
bi- plus lingua 'language' plus adj. ending yields bilingue 'bilingual'

new formations:

bi- plus vita plus -ate yields bivitate 'two-lived, having two lives'
bi- plus digito 'finger' plus adj. ending yields bidigite 'two-fingered'
bi- plus franger 'to break' yields bifranger 'to break twice'

Note: The form di- is used as a synonym of bi- especially in technical terms.


semi- plus deo 'god' yields semideo 'half-god'
semi- plus official yields semiofficial
semi- plus somno 'sleep' plus adj. ending yields semisomne 'half asleep'

new formations:

semi- plus professor yields semiprofessor
semi- plus occider 'to kill' yields semioccider 'to half kill'
semi- plus interessante 'interesting' yields semiinteressante 'fifty-fifty interesting'

Note: The form hemi- is used as a rarer synonym of semi- especially in technical terms.


tri- plus folio 'leaf' yields trifolio 'trefoil, clover'
tri- plus secar 'to cut' yields trisecar 'to trisect'
tri- plus dimension plus -al yields tridimensional 'three-dimensional'
tri- plus angulo plus adj. ending yields triangule 'three-cornered'


quadri- plus syllabo plus adj. ending yields quadrisyllabe
quadri- plus anno 'year' plus -al yields quadriennal 'four-yearly'

Note: The form tetra-, before vowels tetr- is used as a preferred synonym of quadri- especially in technical terms.

Five, six, seven, eight, twelve:

penta- plus metro yields pentametro 'pentameter'
hexa- plus chordo yields hexachordo 'hexachord'
hepta- plus -archia yields heptarchia 'rule by seven'
octa- plus metro yields octametro 'octameter'
dodeca- plus syllabo plus adj. ending yields dodecasyllabe 'twelve-syllabled'

Note: The forms penta-, hexa-, hepta-, octa-, and dodeca- are used like mono-, di-, and tetra-, that is, especially in technical terms and with the special characteristic that they lose their final -a before a vowel.

Ten, hundred, thousand:

Multiplicative compounds involving 10, 100, and 1000 are important primarily by virtue of their use as expressions of units of measurement in the metric system and its technological extensions. Multiplication by 10, 100, 1000, and 10,000 is expressed by deca-, hecto-, kilo-, and myria- respectively. The parallel forms for multiplication by 1/10, 1/100, and 1/1000 are deci-, centi-, and milli-. The final -a- and -o- in deca-, myria-, and hecto- are dropped before an initial vowel of the second compounding element. New analogical formations are possible whenever required for technological and related needs. The form myria- can be used in general (nontechnical) formations with the meaning 'a great many.' A traditional illustration is: litro 'liter,' decalitro 'ten liters,' decilitro 'one tenth of a liter,' hectolitro 'a hundred liters,' centilitro 'one hundredth of a liter,' kilolitro 'a thousand liters,' millilitro 'one thousandth of a liter,' myrialitro ~ten thousand liters.' A possible analogical formation is unitate 'unit,' decunitate 'ten units,' deciunitate 'one tenth of a unit,' hectunitate 'one hundred units,' centiunitate 'one hundredth of a unit,' kilounitate 'one thousand units,' milliunitate 'one thousandth of a unit,' myriunitate 'ten thousand units.'


multi- plus million + -ario yields multimillionario
multi- plus polo 'pole' plus -ar yields multipolar
multi- plus lobo 'lobe' plus adj. ending yields multilobe 'multilobed'

new formations:

multi- plus cyclo yields multicyclo 'cycle with more than three wheels'
multi- plus linea 'line' plus -ate yields multilineate 'many-lined'

Note: The form poly- is used as a synonym of multi- especially in technical terms. To express plurality in the sense of multiplication by several rather than by many, the form pluri- is preferred.


The COLLECTIVE NUMERALS are formed after the model of dozena 'dozen' with the suffix -ena attached to the simple cardinals

Illes arrivava in centenas
'They arrived in groups of a hundred'

Illos se vende in decenas
'They are sold in batches of ten'

Note: A complete set of collectives would have no practical importance but is theoretically possible. If wanted, the first two would have to be formed irregularly as bina 'a group of two' and trina 'a group of three.'


ADVERBIAL NUMERALS are derived from the ordinals either by the normal adverbial suffix -mente or by the ending -o which takes the place of the final -e of adjectives: tertio 'thirdly'; ultimo 'lastly'; etc.

Post toto, ille es primemente mi fratre e secundemente mi adversario politic
'After all, he is first my brother and secondly my political opponent'

Ecce tres possibilitates: Primo, mi opinion es absurde; secundo, mi opinion es theoricamente correcte sed impractic; e tertio, mi opinion es tanto correcte como practic.
'There are three possibilities: First, my view is absurd; second, my view is theoretically correct but impractical; and third, my view is as correct as practical'

Expressed in Arabic numerals the numeral adverbs differ from ordinals in that they end in -o: 1mo, 2ndo, 3tio, etc. See §125 above.


The FUNCTIONS OF NUMERALS differ little from English usage. As in English one may for instance say, capitulo tres 'chapter three' or le tertie capitulo 'the third chapter.' However, in the numbering of sovereigns, contrary to English usage, appositional cardinals are used except in the case of the first where a following substantivized ordinal without article is used.

Napoleon III (Napoleon Tres)
'Napoleon the Third'

Henrico LXVII de Reuss (Henrico Sexanta-Septe)
'Henry the Sixty-Seventh of Reuss'

Frederico I (Frederico Primo)
'Frederic the First'

Catharina I (Catharina Prima)
'Catherine the First'


In DATES the day of the month is indicated by a cardinal. For the first day a substantivized ordinal is permissible.

le 1 de januario (le un de januario)
'the first of January'

le 12 de novembre (le dece-duo de novembre)
'the twelfth of November'

Heri esseva le vinti-octo de februario e hodie es le vinti-nove. - No, hodie es le prime de martio
'Yesterday was the twenty-eighth of February and today is the twenty-ninth. - No, today is the first of March.'


The TIME OF DAY is stated after the following models:

il es un (hora); a un (hora)
'it is one (o'clock); at one (o'clock)'

il es tres (horas); a tres (horas)
'it is three (o'clock); at three (o'clock)'

dece (horas) e quarte
'a quarter past ten (o'clock)'

dece (horas) minus quarte
'a quarter to ten (o'clock)'

dece (horas) e medie
'half past ten (o'clock)'

dece (horas) e vinti (minutas)
'twenty (minutes) past ten (o'clock)'

dece (horas) minus vinti (minutas)
'twenty (minutes) of ten (o'clock)'

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