Parts and Numbers
Esperanto Word-Building
Chapter 7 · Parts, Numbers and Fractions
➗ Parts and Numbers — Partoj kaj nombroj
Esperanto builds its number words the same way it builds everything else. One suffix gives a piece of a whole, three attach to numerals to make fractions, groups and multiples, and one, -um-, has no fixed meaning at all. The chapter shows what each does, and where the dictionary tells you to use a different word instead.
-er-: one piece of a whole
ReVo defines -er- as one of the constituent elements of a whole:
| Word | Parts | Meaning |
|---|---|---|
| akvero | akv + er + o | a drop of water |
| lignero | lign + er + o | a wood chip |
| foliero | foli + er + o | a single leaf |
The bare word ero means an element or particle. ReVo also records a rare sense of something happening once, briefly or unexpectedly, as in tremeri (to shiver briefly), which it links to the prefix ek- from Chapter 2.
-on-: fractions
The suffix -on- attaches only to numerals. The number of equal parts is the base numeral:
| Word | Parts | Meaning |
|---|---|---|
| duono | du + on + o | a half |
| kvarono | kvar + on + o | a quarter |
| kvinono | kvin + on + o | a fifth |
| seponoj | sep + on + oj | sevenths |
A fraction with a numerator is written with the numerator first: ReVo's example is ok estas kvar kvinonoj de dek (eight is four fifths of ten). So three quarters is tri kvaronoj. A long numeral can carry the suffix too: tricent-sesdek-kvinono is one 365th, a day's share of a year.
-op-: a group of that many
On a numeral, -op- makes a collective: duope (two together), triope (three together), kvarope (four together). With other endings the same stem gives adjectives and adverbs meaning "in a group" or "collectively".
-obl-: times as much
The suffix -obl- means "-fold", or exactly so many times the quantity of the root:
| Word | Meaning |
|---|---|
| duobla | double, twofold |
| duoble | twice (as much) |
| kvaroblo | a quadruple, four times a number |
| centoble | a hundred times |
The ReVo examples are mathematical: dudek estas la kvaroblo de kvin (twenty is four times five) and sepoble tri estas dudek unu (seven times three is twenty-one). Note the difference from -foje (times, occasions): dufoje is "twice, on two occasions", duoble is "twice as much".
-um-: the suffix with no fixed meaning
ReVo says Zamenhof noted that -um- has no defined meaning, so its words have to be learned one at a time. The dictionary lists several areas where it appears:
| Area | Examples |
|---|---|
| an extension or special sense of a root | foliumi (to leaf through), ventumi (to fan) |
| a covering for a part of the body | kolumo (a collar), manumo (a cuff) |
| an action with a body part | brakumi (to embrace) |
| supplying or treating with a substance | akvumi (to water) |
📖 A Short Text — Mallonga teksto
Find each number suffix and say what it adds.
Ĉe la tablo
Show a translation
I ate half of the bread and a quarter of the cheese. Twice as many people came as I expected, and four of us sat together at the table.
✏️ Try It Yourself — Ekzercoj
Say the answer first, then click to check.
1. What is the suffix for a single piece of a whole? Give two examples.
Show answer
-er-: akvero (a drop of water), foliero (a leaf).
2. Say in Esperanto: a half, a quarter, a fifth.
Show answer
duono, kvarono, kvinono.
3. Say "three quarters" and "four fifths".
Show answer
tri kvaronoj and kvar kvinonoj.
4. What does triope mean, and what should you use for "in threes"?
Show answer
triope means "three together". For "in threes" ReVo recommends po tri.
5. Translate: "Twenty is four times five."
Show answer
Dudek estas la kvaroblo de kvin.
6. What is the difference between dufoje and duoble?
Show answer
dufoje is twice, on two occasions; duoble is twice as much.
7. Why is it unsafe to build your own word with -um-?
Show answer
Because it has no fixed meaning (ReVo, citing Zamenhof): each -um- word must be learned separately, and overuse blurs clearer suffixes.
8. Match the meaning to the word: collar, to embrace, to leaf through.
Show answer
kolumo, brakumi, foliumi.
9. Take apart kvarono and duobla.
Show answer
kvar + on + o (a quarter); du + obl + a (double).
10. Write two sentences about sharing food, using one fraction and one multiple.
Show answer
One possibility: Mi donis duonon de la kuko al Maria. Ŝi manĝis duoble pli ol mi. (I gave half of the cake to Maria. She ate twice as much as I did.)
Words used in this chapter
akvero drop · duono half · kvarono quarter · duope two together · duoble twice as much · kolumo collar · brakumi embrace · po each · pano bread · fromaĝo cheese · atendi expect · tablo table · kuko cake