The ordinary Esperanto noun ends in -o: domo “house,” amiko “friend,” muziko “music,” amo “love.” This ending tells you the word is presenting a person, thing, substance, event, quality, or idea as a noun. It is part of a productive system, not an arbitrary final vowel you can omit.
After -o, add -j for plural and -n for the accusative or another licensed n-role. If both appear, the order is fixed: root + o + j + n. The broader phrase system is introduced on noun-phrase anatomy.
The noun citation form
Dictionaries commonly present an ordinary noun in its singular non-accusative form: radiko + o. This citation form names the lexical item without yet marking plural or object function.
| Root | Noun | Basic noun meaning |
|---|---|---|
| dom- | domo | house |
| hund- | hundo | dog |
| am- | amo | love |
| kur- | kuro | a run / act of running |
| bel- | belo | beauty as a noun |
| martel- | martelo | hammer |
La hundo dormas apud la pordo.
The dog is sleeping beside the door.
Amo kaj paco gravas en ĉiu komunumo.
Love and peace matter in every community.
An o-word can name something concrete, abstract, animate, inanimate, countable, or non-countable. The ending marks noun status; it does not by itself mean “physical object.”
One root, several grammatical views
Esperanto can attach different category endings to a stable root. Compare laboro “work” as a noun, labori “to work,” labora “work-related,” and labore “by working / in relation to work.” The exact meanings become conventional with use, but the ending consistently tells you how the word functions.
La laboro estas malfacila, sed mi ŝatas labori ekstere.
The work is difficult, but I like working outside.
Laboro names the work; labori presents the activity as a verb. This is a minimal formal contrast with a real grammatical consequence.
La belo de la ĝardeno surprizis la vizitantojn.
The beauty of the garden surprised the visitors.
Belo turns the quality root bel- into a noun. The related adjective is bela ĝardeno, “beautiful garden.” English often uses unrelated forms such as beautiful/beauty; Esperanto lets the category ending expose the relationship.
Singular and plural: -o versus -oj
An ordinary count noun without -j is singular. Add -j after -o when there is more than one: libro → libroj, seĝo → seĝoj. Esperanto keeps -j even when a number or quantity word already shows plurality.
Unu gasto atendas, sed tri gastoj jam sidas ĉe la tablo.
One guest is waiting, but three guests are already sitting at the table.
Ĉu vi aĉetis du librojn aŭ nur unu libron?
Did you buy two books or only one book?
The number du does not replace plural -j. This differs from languages that leave the noun singular after numerals.
Plural can also mean varieties or separate instances. A normally substance-like noun such as vino is usually singular for wine as material, but vinoj can mean several wines or kinds of wine.
La restoracio proponas tri lokajn vinojn.
The restaurant offers three local wines.
The plural does not magically make liquid countable; the context supplies an interpretation such as kinds, servings, or products.
Accusative -n comes last
Add -n after the noun’s number ending when the noun phrase is a direct object: libron for one book, librojn for several books. The sequence is always -o-j-n, never -o-n-j.
| Number | Non-accusative | Accusative |
|---|---|---|
| singular | libro | libron |
| plural | libroj | librojn |
La infano trovis ŝlosilon sub la seĝo.
The child found a key under the chair.
Infano is the subject and has no -n. Ŝlosilon is the object of trovis and ends in -on.
La instruisto montris la novajn mapojn.
The teacher showed the new maps.
Mapojn contains map-o-j-n. The directly describing adjective agrees, but adjective agreement belongs on its dedicated pages.
Count and mass meanings
Countability follows meaning and usage, not English grammar. Akvo, lakto, rizo, sablo, muziko normally denote undivided substances or activities and therefore usually stay singular. To count portions or containers, add a measure phrase: du glasoj da akvo, not automatically du akvoj.
Ni bezonas akvon kaj du kilogramojn da rizo.
We need water and two kilograms of rice.
Some nouns shift between individual and substance readings. Fiŝo may name one fish, while in a food context it can mean fish as food. Plural fiŝoj clearly presents multiple individual fish or kinds.
En la lago naĝas multaj fiŝoj, sed mi ne manĝas fiŝon.
Many fish are swimming in the lake, but I do not eat fish.
English transfer works in both directions. English advice is normally mass, but Esperanto konsilo is a countable recommendation and readily forms konsiloj.
Ŝi donis al mi du utilajn konsilojn.
She gave me two useful pieces of advice.
See count and mass meanings for the semantic details.
Article, gender, and proper-name boundaries
Esperanto has no indefinite article corresponding to English a/an: Mi aĉetis libron means “I bought a book.” The definite article la does not change form for number or case.
Mi serĉas hotelon; la hotelo apud la stacio estas plena.
I’m looking for a hotel; the hotel by the station is full.
The -o ending does not mark masculine gender. Amiko, instruisto, kuracisto can be gender-neutral where context permits. Natural sex and explicit gender vocabulary are separate lexical topics.
Fully Esperantized proper names often behave like o-words—Petro, Berlino—but foreign-form names may lack -o and follow special conventions. That exception does not weaken the ordinary noun rule.
Elision is marked, not neutral prose
The Fundamental apostrophe can replace final -o when no -j or -n follows: kor’ for koro. This is (literary/poetic) in modern use, not the normal A1 citation form. It remains singular, and its stress is calculated as though the missing o were present.
En la poemo aperas «kor’», sed en ordinara prozo mi skribas «koro».
The form kor’ appears in the poem, but in ordinary prose I write koro.
A short exchange
— Ĉu vi bezonas unu seĝon aŭ du seĝojn? — Du seĝojn, mi petas.
— Do you need one chair or two chairs? — Two chairs, please.
The reply carries both plural -j and object -n, even though du already supplies the number.
Common Mistakes
1. Omitting -o from a complete noun. A bare root is not normally an independent noun.
❌ Mi aĉetis novan libr.
Incorrect — the noun root lacks the -o ending and accusative -n.
✅ Mi aĉetis novan libron.
I bought a new book.
2. Omitting -j after a number. Number words do not suppress plural marking.
❌ Sur la tablo estas tri libro.
Incorrect — libro remains singular after tri.
✅ Sur la tablo estas tri libroj.
There are three books on the table.
3. Omitting object -n. Word order does not replace case marking.
❌ La infano trovis la ŝlosilo.
Incorrect — the direct object lacks -n.
✅ La infano trovis la ŝlosilon.
The child found the key.
4. Putting -n before -j. The fixed order is -ojn.
❌ Ŝi legis la libronj.
Incorrect — plural j has been placed after accusative n.
✅ Ŝi legis la librojn.
She read the books.
5. Copying English countability mechanically. Learn the Esperanto noun’s ordinary meaning.
❌ Li donis al mi du konsilo.
Incorrect — konsilo is countable and must be plural and accusative here.
✅ Li donis al mi du konsilojn.
He gave me two pieces of advice.
Key Takeaways
Use -o to form the ordinary noun citation form, then add -j for plural and final -n for accusative: -o, -oj, -on, -ojn. The root remains available for other categories. Number and countability follow Esperanto meaning, not English habits, and poetic apostrophe is a marked alternative rather than the neutral noun form.
Related Topics
- Singular and Plural NounsA1 — How Esperanto builds singular, plural, and accusative noun forms from a stable root using -o, -j, and -n.
- Noun Phrase AnatomyA1 — How determiners, numbers, adjectives, an -o head noun, and postmodifiers combine into a complete Esperanto noun phrase.
- Count and Mass MeaningsA1 — How Esperanto distinguishes countable individuals from unbounded substances and shifts nouns between those meanings.
- The Accusative -N: OverviewA1 — Understand how Esperanto uses final -n to mark direct objects, direction, time, and measurement without relying on word order.
- Roots and Grammatical EndingsA2 — See how Esperanto combines meaningful roots with noun, adjective, adverb, and verb endings to create usable words.
- Adjectives and the -A EndingA1 — How the productive -a ending creates describing words and how adjectives agree, modify nouns, and function after esti.