Esperanto Fractions, Multiples and Groups: -on-, -obl-, -op-

Three suffixes turn any number into a new word: one for a fraction, one for a multiple, one for a group. The usual endings then do their usual jobs.

The three suffixes on one screen

Each in a sentence:

• Mi manĝis duonon de la pano. - I ate half of the bread.
• Li pagis duoble. - He paid double.
• Ili venis duope. - They came in twos.

English has half, quarter, double and triple as separate words, then gives up and says one seventeenth. These suffixes attach to any number, so centono (a hundredth) and centobla (hundredfold) need no dictionary entry.

Fractions with -on-

The ending says the job, as on any root:

• duona horo - half an hour
• Ĝi estas duone plena. - It is half full.
• tri kvaronoj - three quarters

Multiples with -obl-

The adverb in -e is often the natural form, and -ig- makes a verb:

• Mi pagis duoble. - I paid double.
• Ili duobligis la prezon. - They doubled the price.

Groups with -op-

-op- means in a group of that many, usually as an adverb in -e:

• Ili laboris duope. - They worked in twos.
• La infanoj eniris triope. - The children came in in threes.
• Ni iris kvarope. - We went in fours.

As a noun, duopo is a pair or a duo.

Numbers as nouns: dekduo, centoj

A plain -o on a number makes a noun for a group of that size. As nouns they take -j and link with da:

Note dekduo is one word, while the number twelve is dek du.

po: so many each

Po shares a number out: so many each.

• Mi donis al la infanoj po tri libroj. - I gave the children three books each.
• La pomoj kostas po unu eŭro. - The apples cost one euro each.

Po is a preposition, so tradition leaves the noun after it without -n: po tri libroj. You will also meet po tri librojn in good writing, because the phrase feels like the object; PMEG calls both correct, and this site writes it without. More in tricky prepositions.

Keep po and -op- apart:

Mistakes English speakers make

What to do next

1. Build the fraction, multiple and group of kvar.
2. Say how much of something you ate today with duonon or kvaronon.
3. Then read numbers again for the ordinals with -a.

See also

• Numbers - the nine roots, the join rule and the ordinals.
• Quantity - iom, multe and the da rule in full.
• Tricky prepositions - po and the argument about its accusative.
• Word building - the other suffixes, which work exactly like these.