Esperanto nouns and adjectives: -o, -a and plural -j

Every Esperanto noun ends in -o and every adjective in -a. Both add -j for the plural and -n for the object, and an adjective always matches its noun: bona kato, bonaj katoj, bonan katon, bonajn katojn – "good cat(s)". There is no grammatical gender and no irregular plural.

#Nouns: the -o ending

A noun is any word ending in -o: domo – "house", amiko – "friend", kuro – "a run". The ending shows the word class, so one root gives several words: bela – "beautiful", bele – "beautifully", belo – "beauty". This is the basis of Esperanto word building.

belonoun

-obelonoun-abelaadjective-ebeleadverb-ibeliinfinitive

Nouns have no grammatical gender. Most words for people, like amiko – "friend" or instruisto – "teacher", say nothing about sex. A few roots are male by meaning, and the suffix -in- makes the female form: patro – "father", patrino – "mother". See suffixes.

#The plural: -j

Add -j after the ending: domo → domoj – "houses", bela → belaj. The ending -oj sounds like "oy" in "boy", and -aj like "eye".

After any number above one, the noun is plural: du katoj – "two cats", tri grandaj domoj – "three big houses". With unu – "one", it stays singular: unu tago – "one day".

#Agreement: the adjective copies its noun

An adjective takes the same -j and -n as the noun it describes. This is the complete pattern:

• La bonaj katoj dormas. – "The good cats are sleeping."
• Mi vidas bonajn katojn. – "I see good cats."

The order never changes: ending, then -j, then -n. So katojn, never katonj. The plural object ending -ojn rhymes with English "coin". When to add -n is explained on the accusative.

Words that work like adjectives agree in the same way. This includes possessives such as mia – "my" and correlatives such as tiu – "that": miajn amikojn – "my friends" (object), tiujn librojn – "those books" (object). See pronouns and correlatives.

#Position of the adjective

The adjective usually comes before the noun, but after the noun is also correct: bela domo or domo bela – "a beautiful house". The endings show which noun it belongs to, even when the word order changes.

#Adjectives after esti

After esti – "to be", iĝi – "to become" and ŝajni – "to seem", the adjective agrees in number but never takes -n:

• La katoj estas bonaj. – "The cats are good."
• La domo ŝajnas malnova. – "The house seems old."

One adjective describing two singular nouns joined by kaj – "and" is plural: La tablo kaj la seĝo estas novaj. – "The table and the chair are new."

#Comparison: pli, plej, ol

Esperanto has no comparative endings and no irregular forms like "good – better – best". Short words do the job:

Bona stays regular: pli bona – "better", la plej bona – "the best". The same words compare adverbs: pli rapide – "faster".

After ol and kiel, a word keeps the role it would have in the full sentence:

• Mi amas vin pli ol li. – "I love you more than he does."
• Mi amas vin pli ol lin. – "I love you more than (I love) him."

For "very" and "too", use tre and tro: tre granda – "very big", tro granda – "too big". The suffixes -eg- and -et- change strength inside the word: granda → grandega – "huge", domo → dometo – "cottage".

#Common mistakes

#Common questions

#Do Esperanto adjectives agree with nouns?

Yes, in number and case. If the noun has -j or -n, so does every adjective describing it: grandajn domojn – "big houses" (object). There is no gender agreement, because there is no grammatical gender.

#How do you form the plural in Esperanto?

Add -j to the noun and to its adjectives: nova libro → novaj libroj – "new books". There are no exceptions.

#How do you say "better" and "best" in Esperanto?

Pli bona is "better" and la plej bona is "the best". For adverbs: pli bone – "better", plej bone – "best".

#Can an adjective come after the noun?

Yes. Domo bela and bela domo are both correct; the endings show which words belong together.

#Sources

• Fundamento de Esperanto, rules 2 and 3 (English) – Akademio de Esperanto
• Seksa signifo de O-vortoj – PMEG
• A-vortoj: bazaj reguloj – PMEG
• Nombro: bazaj reguloj and Nombro ĉe A-vortoj – PMEG
• N-finaĵo: bazaj reguloj – PMEG
• Kiel kaj ol: uzado and kun rolmontriloj – PMEG
• Esperanto grammar – Wikipedia