The official suffix -op- presents a number as the size of a group. Duopo is one group containing two members, duopa describes something consisting of two members, and duope means “together in a group of two” or “in groups of two.” This grouping meaning differs from a bare cardinal, distributive po, and multiplicative -obl-. The broader derivational pattern is mapped on the dedicated suffix -op- page.
One suffix, three useful forms
Attach -op- to a number and add the ending required by the sentence:
| Form | Function | Core meaning |
|---|---|---|
| triopo | noun | a group of three |
| triopa | adjective | consisting of three members |
| triope | adverb | together/in groups of three |
En la angulo ludis triopo da muzikistoj.
A trio of musicians was playing in the corner.
La universitatoj kreis triopan esplorgrupon por la projekto.
The universities created a three-member research group for the project.
La partoprenantoj diskutis triope dum dek minutoj.
The participants discussed in groups of three for ten minutes.
In each example, tri states the membership count inside a group. It does not simply count independent musicians, institutions, or discussions.
Bare cardinal versus an -op- group
Compare simple quantity with a grouped unit:
Tri muzikistoj atendis apud la scenejo.
Three musicians were waiting beside the stage.
Triopo da muzikistoj atendis apud la scenejo.
A group of three musicians was waiting beside the stage.
The first merely counts people. The second asks the listener to view those people as one three-member group. That difference affects agreement: tri muzikistoj atendis has a plural subject, while triopo ... atendis has the singular head triopo.
An -op-o word is an ordinary noun and can take case and plural endings:
La organizantoj elektis du kvaropojn por la fina rondo.
The organizers selected two groups of four for the final round.
Kvaropojn is plural accusative because two separate four-person groups were selected. The total number of people is eight, but the grammar foregrounds two units, not eight individuals.
When the members are named after the group noun, da is natural because the head expresses a quantity-like group: kvaropo da studentoj. If the members are definite, a de phrase can identify composition or association: la kvaropo de nia klaso “our class's group of four.”
Duo, trio, and explicit duopo, triopo
Number words with -o can themselves name a number or a group: duo can mean the number two or a pair/group of two, and trio can mean the number three or a trio. Therefore duopo and triopo are not always obligatory.
La kantista duo publikigos novan albumon en Novembro.
The singing duo will release a new album in November.
La triopo de finalistoj atendis la rezulton kune.
The trio of finalists waited for the result together.
In established labels such as a musical duo or trio, the shorter noun is especially common. The transparent -op- form remains productive and makes group size explicit even where no lexicalized label exists: kvinopo, dekopo, dekduopo.
Paro is another conventional word for two things viewed together. Use it when the pairing itself is familiar—paro da ŝuoj, geedza paro. Duopo is the systematic numerical term and works well for a deliberately formed team or group.
The adverbs unuope, duope, triope
The adverb describes how participants act or are arranged:
Bonvolu eniri unuope, por ke ni povu kontroli la biletojn.
Please enter one at a time so that we can check the tickets.
La infanoj revenis duope de la ludejo.
The children returned in pairs from the playground.
Ni laboros kvarope: du homoj esploros kaj du verkos.
We will work as a group of four: two people will research and two will write.
Unuope is not simply the number one; it presents each person separately. The adjective unuopa likewise means an individual member viewed separately:
Ni ne publikigos unuopajn respondojn, nur la komunan rezulton.
We will not publish individual responses, only the combined result.
In neutral contemporary usage, these forms are common wherever group organization matters: classrooms, games, teams, seating, and administrative procedures.
-op- versus po
Both can be translated with English “in twos” or “two each,” but their grammatical viewpoint differs. Duope describes the grouping or manner. Po du distributes an equal quantity to repeated recipients, places, or occasions:
La gastoj sidis duope ĉe la malgrandaj tabloj.
The guests sat in pairs at the small tables.
Ni metis po du seĝojn ĉe ĉiu tablo.
We put two chairs at each table.
The first tells how the guests were grouped. The second assigns two chairs to every table. They can occur together when both meanings matter:
La kursanoj laboris duope kaj ricevis po unu demandaron por ĉiu paro.
The course participants worked in pairs and received one questionnaire per pair.
English often leaves distribution implicit. Esperanto po explicitly says that the same number recurs across units; -ope focuses on the members acting together.
-op- versus -obl-
-Op- counts members in a group. -Obl- expresses multiplication or multiple layers/parts:
La komisiono estas kvinopa.
The committee has five members.
La skatolo havas kvinoblan protektan tavolon.
The box has a fivefold protective layer.
A duopa lito would compositionally suggest a two-member arrangement, but the conventional expression for a bed designed for two is duobla lito. Word formation is regular, yet conventional vocabulary still matters; not every mathematically possible derivative is the usual term for a familiar object.
PMEG's useful diagnostic is that an object made of two corresponding parts, each itself resembling the whole kind of object, normally takes -obl-, not -op-. Groups of people or independent members take -op-.
Asking about group size
The productive question is kiomope? “in groups of how many?” or “how many together?”
— Kiomope ni faru la ekzercon? — Triope, sed la lasta grupo havos kvar homojn.
— In groups of how many should we do the exercise? — In threes, but the last group will have four people.
Multope means “in a large group” or “many together,” without specifying a number:
La vizitantoj alvenis multope tuj post la malfermo.
Visitors arrived in large numbers just after opening.
These extensions show that -op- combines not only with exact numerals but also with number-like quantity words.
Spelling and larger groups
As with -obl- and -on-, join the whole numeral to the suffix. Write dekduopa for twelve-member and use clarifying hyphens for a longer structure: dudek-kvinopa delegacio. A space changes the structure:
La kongreso akceptis dudek kvinopajn teamojn.
The congress accepted twenty five-person teams.
La kongreso akceptis dudek-kvinopan delegacion.
The congress accepted a twenty-five-member delegation.
The first has cardinal dudek modifying plural kvinopajn teamojn. The second has one adjective based on twenty-five. In documents where the distinction matters, hyphens make it visible.
Common Mistakes
Using an -op- form for simple counting
❌ Mi aĉetis triopon da pomoj por la recepto.
Unnatural if you simply mean three apples rather than a deliberately grouped set.
✅ Mi aĉetis tri pomojn por la recepto.
I bought three apples for the recipe.
Confusing grouping with repetition
❌ La lernantoj legis la dialogon dufoje.
Wrong if they read it together in pairs; this says they repeated the reading twice.
✅ La lernantoj legis la dialogon duope.
The students read the dialogue in pairs.
Confusing grouping with distribution
❌ Ni donis duope krajonojn al ĉiu infano.
Incorrect for two pencils per child — duope describes participants grouping together.
✅ Ni donis po du krajonojn al ĉiu infano.
We gave two pencils to each child.
Forgetting that an -op-o form is a noun
❌ La trejnisto elektis du triopo por la matĉo.
Incorrect — two separate groups require plural accusative marking.
✅ La trejnisto elektis du triopojn por la matĉo.
The coach selected two groups of three for the match.
Writing a derived group number as separate words
❌ Ili formis dek du opan komitaton.
Incorrect spacing for one twelve-member committee.
✅ Ili formis dekduopan komitaton.
They formed a twelve-member committee.
Key Takeaways
Use -op-o for a group as a noun, -op-a for something consisting of that many members, and -op-e for acting or arranging in groups of that size. Keep simple cardinals for mere quantity, po for equal distribution, fojo for repeated occasions, and -obl- for multiplication or layered structure.
Related Topics
- Cardinal NumbersA1 — Use Esperanto cardinal numbers to count, quantify noun phrases, identify items, and read basic dates, times, measurements, and decimal notation.
- Multipliers and RepetitionsA2 — Distinguish multiplication with -obl- from repeated occasions with fojo, and form each pattern productively.
- Numbers as Nouns, Adjectives, and AdverbsB2 — Change Esperanto number words into nouns, adjectives, and adverbs while preserving the distinction between quantity, order, and manner.
- -op-: Groups Of A Stated NumberB1 — Use -op- to turn a number into a group size, distinguishing members acting together from simple counting, distribution, repetition, and multiplication.
- Collective NounsB1 — How singular Esperanto nouns name groups, how -ar- builds collections, and when a collective itself becomes plural.
- PoB2 — Use po before a repeated quantity to distribute equal shares, rates, or amounts across people, things, places, or occasions.