Numbers
Complete Esperanto number reference — cardinals, ordinals, multiplicatives, fractions, collectives, distributive po, and arithmetic vocabulary.
Overview
Esperanto numbers are simple and fully systematic. Cardinal numbers are invariable — they never take plural -j or accusative -n. Only the nouns and adjectives following them take normal agreement. The exceptions are miliono and miliardo, which are regular nouns (they do take -j and -n). Beyond cardinals, a system of suffixes generates ordinals, multiplicatives, fractions, and collectives from the same roots.
Cardinal Numbers (Basic)
| Number | Esperanto |
|---|---|
| 0 | nulo |
| 1 | unu |
| 2 | du |
| 3 | tri |
| 4 | kvar |
| 5 | kvin |
| 6 | ses |
| 7 | sep |
| 8 | ok |
| 9 | naŭ |
| 10 | dek |
| 11 | dek unu |
| 12 | dek du |
| 20 | dudek |
| 21 | dudek unu |
| 30 | tridek |
| 40 | kvardek |
| 50 | kvindek |
| 60 | sesdek |
| 70 | sepdek |
| 80 | okdek |
| 90 | naŭdek |
| 100 | cent |
| 200 | ducent |
| 1,000 | mil |
| 2,000 | du mil |
| 1,000,000 | unu miliono |
| 1,000,000,000 | unu miliardo |
Compound Cardinal Numbers
Compound numbers are formed by writing the components in order from largest to smallest, without connectors:
- 21 → dudek unu
- 35 → tridek kvin
- 142 → cent kvardek du
- 1,999 → mil naŭcent naŭdek naŭ
- 2,500 → du mil kvincent
- 1,000,000 → unu miliono (or simply miliono)
Hundreds: Form hundreds by placing the number directly before cent: ducent (200), tricent (300), kvarcent (400).
Thousands: Write the multiplier before mil: du mil (2,000), dek mil (10,000), cent mil (100,000).
Grammar of Cardinal Numbers
Cardinal numbers (unu through any compound) are invariable particles — they receive no endings:
tri libroj — three books (libroj takes the plural -j, but tri does not change) mi vidis kvin homojn — I saw five people (homojn takes accusative + plural, but kvin does not change) dudek unu studento — twenty-one students (studento takes no plural here — see below)
Agreement with the following noun: A noun after a cardinal number takes the case required by the sentence, but the plural -j is optional after a numeral because the number itself already indicates plurality. Both of these are correct:
- tri libroj (three books — with plural)
- tri libro (three books — without plural, the number makes it clear)
Both forms are standard. The plural is more common in careful written style.
Miliono and Miliardo: Regular Nouns
Miliono (million) and miliardo (billion) are regular nouns with the -o ending. They take normal noun agreement:
- du milionoj — two million (plural)
- mi havas tri milionojn — I have three million (accusative + plural)
- kelkaj milionoj da homoj — several millions of people
After miliono and miliardo, use the preposition da (of/worth of, used after quantities): kvin milionoj da dolaroj — five million dollars
The da rule: after expressions of quantity (numbers of millions, liters, kilograms, etc.), use da before the noun counted: glaso da akvo (a glass of water), kilogramo da sukero (a kilogram of sugar).
Ordinal Numbers: the -a Suffix
Ordinal numbers are formed by adding the adjective ending -a to the cardinal:
| Cardinal | Ordinal | Meaning |
|---|---|---|
| unu | unua | first |
| du | dua | second |
| tri | tria | third |
| kvar | kvara | fourth |
| kvin | kvina | fifth |
| ses | sesa | sixth |
| sep | sepa | seventh |
| ok | oka | eighth |
| naŭ | naŭa | ninth |
| dek | deka | tenth |
| dudek | dudeka | twentieth |
| cent | centa | hundredth |
| mil | mila | thousandth |
Ordinals are regular adjectives — they take -j (plural) and -n (accusative) as required:
la unua tago — the first day la unuaj tagoj — the first days mi amas la duan tagon — I love the second day
Usage: Ordinals are used for ordering, dates, chapter numbers, and monarchs: la tria de marto — the third of March Elizabeto la Dua — Elizabeth the Second Ĉapitro kvar — Chapter four (cardinal also acceptable for chapters)
Multiplicatives: the -obl- Suffix
The suffix -obl- means "times / -fold":
| Root | With -obl- | Meaning |
|---|---|---|
| unu | unuobla | single, onefold |
| du | duobla | double, twofold |
| tri | triobla | triple, threefold |
| kvar | kvarobla | quadruple |
| dek | dekobla | tenfold |
duobla porco — double portion triobla salto — triple jump
As a verb (with -igi / -iĝi): duobligi — to double (something) triobliĝi — to triple (to become three times as much)
As an adverb: duoble — doubly, twice as much
Fractions: the -on- Suffix
The suffix -on- means "one [number]-th part" — it creates fraction nouns:
| Root | With -on- | Meaning |
|---|---|---|
| du | duono | half |
| tri | triono | third (one-third) |
| kvar | kvarono | quarter |
| kvin | kvinono | fifth |
| dek | dekono | tenth |
| cent | centono | hundredth, percent (one percent) |
Fractions are nouns (ending in -o) and take normal noun agreement: duono de la torto — half of the cake du trionoj — two thirds tri kvaronojn — three quarters (accusative)
Common use: duono (half) is extremely frequent: duona horo (half an hour, adjective form with -a), duone (halfway, adverb with -e).
Percentages: dekono = 10%, centono = 1% (literally "one hundredth"). More commonly expressed as procentoj: dek procentoj (ten percent).
Collective Numerals: the -op- Suffix
The suffix -op- creates collective numerals that describe groups acting together. They are used as adverbs (ending in -e):
| Root | With -op- | Meaning |
|---|---|---|
| du | duope | in a pair, two by two / two of them together |
| tri | triope | in a group of three, three together |
| kvar | kvarope | four together |
| kvin | kvinope | five together |
Ni iris duope. — We went as a pair / the two of us went. Ili venkis triope. — They won, the three of them together. La infanoj ludis kvarope. — The children played in groups of four.
The collective suffix emphasizes the group acting as a unit, not the individual count.
Distributive po: Each / Apiece
po is a special preposition (some call it a particle) meaning "each / apiece / at a rate of." It distributes a quantity across multiple recipients or instances:
Mi donis al ĉiu po tri pomoj. — I gave each one three apples (three apples each). Ili ricevis po dek eŭrojn. — They received ten euros each. La trejnoj foriras po du horojn. — The trains depart every two hours (at two-hour intervals). Ŝi aĉetis po kvin olivojn. — She bought five olives apiece (per serving/item).
Note: The noun after po takes the accusative if the overall sentence has accusative context: Mi pagis po du eŭrojn por ĉiu libro. — I paid two euros each for each book.
Arithmetic in Esperanto
| Operation | Esperanto | Example |
|---|---|---|
| Addition (+) | plus or kaj | Du plus tri estas kvin. |
| Subtraction (−) | minus | Dek minus kvar estas ses. |
| Multiplication (×) | fojoj (times) | Tri fojoj kvar estas dek du. |
| Division (÷) | dividite per | Dek dividite per du estas kvin. |
| Equals (=) | estas | ... estas kvin. |
| Squared | kvadrata / duobligita | Tri kvadrata estas naŭ. |
Saying years: mil naŭcent naŭdek kvar = 1994. du mil dudek ses = 2026.
Saying clock time: Use je: je la tria (at three o'clock), je la dek kvara kaj tridek (at 14:30), je la sepa kaj duono (at half past seven).
Saying dates: La tria de marto (the third of March), la unua de januaro du mil dudek ses (1 January 2026).
Complete Number Type Table
| Type | Suffix / Form | Example | Meaning |
|---|---|---|---|
| Cardinal | (no suffix) | tri | three |
| Ordinal | -a | tria | third |
| Multiplicative | -obla | triobla | triple / threefold |
| Fraction | -ono | triono | one third |
| Collective | -ope | triope | in threes / three together |
| Distributive | po + number | po tri | three each |
| Multiplied adverb | -oble | trioble | three times as much |