An Esperanto adjective normally ends in -a: bona “good,” longa “long,” ligna “wooden,” vespera “evening-related.” The ending tells you that the word describes or classifies something. Because roots remain stable, changing the grammatical ending often reveals a family: bel-o “beauty,” bel-a “beautiful,” bel-e “beautifully.”
Adjectives agree with the noun phrase they directly describe. Add plural -j and accusative -n after -a, always in that order: bona, bonaj, bonan, bonajn. This agreement occurs both before or after a noun and in a predicate with esti.
What -a contributes
The general meaning of -a is “characterized by or related to what the root expresses.” The root and context supply the exact relationship:
| Root family | A-word | Typical relationship |
|---|---|---|
| ruĝ-o, redness/red | ruĝ-a | having red as a property |
| lign-o, wood | lign-a | made of wood |
| somero, summer | somer-a | related to or occurring in summer |
| urbo, city | urb-a | related to a city or urban life |
Ni luis malgrandan lignan domon apud la lago.
We rented a small wooden house beside the lake.
Malgranda expresses a property; ligna expresses material. Both use -a because both directly describe domo. As part of the singular direct object, they become malgranda-n ligna-n domo-n.
La somera kurso komenciĝos en Julio.
The summer course will begin in July.
English freely places the noun summer before another noun. Esperanto normally makes the relationship explicit with the A-word somera, or uses a transparent compound when conventional. The ending is productive, but its broad meaning means that context sometimes decides whether the relationship is material, time, purpose, origin, or another association.
The four basic agreement forms
| Form | Use | Example phrase |
|---|---|---|
| -a | singular, no accusative | nova libro |
| -aj | plural, no accusative | novaj libroj |
| -an | singular accusative | novan libron |
| -ajn | plural accusative | novajn librojn |
Nova kafejo malfermiĝis ĉe la stacidomo.
A new café opened near the station.
Du novaj kafejoj malfermiĝis ĉe la stacidomo.
Two new cafés opened near the station.
Ni provis la novan kafejon hieraŭ.
We tried the new café yesterday.
Ni provis la du novajn kafejojn hieraŭ.
We tried the two new cafés yesterday.
This four-way set is the core agreement system. In the final sentence, nova-j-n and kafej-o-j-n both show that they belong to one plural direct-object phrase. The article la and number du remain unchanged. The dedicated pages on Number Agreement and Accusative Agreement develop these two dimensions separately.
Agreement follows phrase membership, not mere proximity. In la fotoj de la malnova domo, malnova describes singular domo, not the nearby plural fotoj.
Mi trovis la fotojn de la malnova domo en tirkesto.
I found the photos of the old house in a drawer.
The object ending belongs to fotojn. The phrase after de has its own structure, so malnova domo is singular and has no accusative.
Before or after the noun
An adjective can appear before or after the noun it directly modifies. Before the noun is a frequent neutral choice; after the noun can add focus, rhythm, contrast, or literary flavor. Position does not remove agreement.
Ŝi portis ruĝan mantelon.
She was wearing a red coat.
Ŝi portis mantelon ruĝan, ne la nigran.
She was wearing a red coat, not the black one.
The second order gives ruĝan contrastive weight. It is grammatical, but learners should not assume that every adjective changes meaning simply by moving. Established combinations and discourse focus matter; neutral adjective-before-noun order is a reliable starting point.
The foundational norm requires the A-ending and agreement, not one rigid position. Both preposed and postposed adjectives are established in actual usage. The preposed order is a pedagogical default for ordinary description; postposition is useful when context gives it a clear contrastive, rhythmic, or (literary) purpose.
Multiple direct adjectives each agree:
Ĉu vi vidis mian malgrandan nigran sakon?
Have you seen my small black bag?
Mian, malgrandan, nigran, and sakon are all singular accusative. The possessive is itself an A-word and participates in agreement, even though it also determines the phrase.
Adjectives after esti
An adjective can be attributive, inside a noun phrase, or predicative, linked to the subject by esti. A predicative adjective still agrees with its subject in number, but it does not take accusative simply because another noun elsewhere in the sentence is an object.
La ĉambro estas hela kaj trankvila.
The room is bright and quiet.
La ĉambroj estas helaj kaj trankvilaj.
The rooms are bright and quiet.
Plural ĉambroj requires plural helaj and trankvilaj. Compare attributive la helaj ĉambroj with predicative la ĉambroj estas helaj: the same property and agreement appear in different syntactic positions.
— Ĉu la fenestroj estas puraj? — Ne, ili ankoraŭ estas tre polvaj.
— Are the windows clean? — No, they are still very dusty.
The exchange includes a question and negative answer. Tre is an adverb and remains unchanged; puraj and polvaj agree with plural fenestroj/ili.
Scope: what exactly does the adjective describe?
An adjective modifies a noun phrase, not automatically every nearby noun. In nova libro pri antikva urbo, nova describes the book and antikva describes the city. Endings help, but prepositions and phrase boundaries determine scope.
Mi aĉetis novan libron pri antikvaj urboj.
I bought a new book about ancient cities.
Novan belongs to the singular object libron. Antikvaj belongs inside the pri phrase with plural urboj, so it has -j but no -n.
Relational adjectives often classify rather than describe a gradable quality. Medicina revuo is a medical journal; urba transporto is urban transport. Saying tre medicina revuo is normally odd because the adjective establishes a category rather than a degree. Whether an A-word is gradable depends on its meaning in context, not on the ending alone.
La universitata biblioteko ricevis novan medicinan revuon.
The university library received a new medical journal.
English uses noun modifiers in university library and medical journal. Esperanto uses the A-words universitata and medicina to show their modifying role.
Adjective ellipsis is not an O-word
When context supplies the noun, an adjective can remain without it: la ruĝa [taso], la ruĝaj [tasoj], la ruĝan [tason]. This is noun ellipsis; the A-word keeps its -a ending and agreement.
La blua ĉemizo estas tro granda, do mi prenos la verdan.
The blue shirt is too large, so I will take the green one.
La verdan means la verdan ĉemizon. Changing the form to verdon would mean the color green or greenness, not “the green one.”
An independent O-word derived from the same root has a noun meaning: bono “goodness/a good,” ruĝo “redness/the color red.” A person noun may use a suffix: junulo “a young person,” riĉulo “a rich person.” Do not treat every bare adjective as an automatic person noun.
La juna kliento atendis ekstere, sed la junulo ĉe la fenestro jam estis servata.
The young customer waited outside, but the young person at the window was already being served.
Juna directly describes kliento. Junulo is a complete O-word formed with -ul- and denotes a person characterized by youth.
Common Mistakes
1. Leaving a plural adjective singular
❌ La nova studentoj atendas ekstere.
Incorrect: the adjective must agree with the plural noun.
✅ La novaj studentoj atendas ekstere.
The new students are waiting outside.
2. Marking the noun but not the adjective as an object
❌ Mi mendis varma supon.
Incorrect: the direct adjective also needs accusative -n.
✅ Mi mendis varman supon.
I ordered hot soup.
3. Matching by proximity instead of phrase membership
❌ Mi legis la artikolojn pri la nova regularojn.
Incorrect: nova belongs with plural regularoj inside the pri phrase, which has no accusative.
✅ Mi legis la artikolojn pri la novaj regularoj.
I read the articles about the new regulations.
4. Copying an English noun modifier
❌ Ŝi laboras en universitato biblioteko.
Incorrect: universitato cannot simply modify biblioteko as an English noun does.
✅ Ŝi laboras en universitata biblioteko.
She works in a university library.
5. Replacing an elliptical adjective with -o
❌ Mi elektis la ruĝon, ne la bluan ĉemizon.
Incorrect for ‘the red one’: ruĝon denotes the color red or redness.
✅ Mi elektis la ruĝan, ne la bluan ĉemizon.
I chose the red one, not the blue shirt.
Key Takeaways
The productive ending -a forms words that describe or classify. Direct adjectives agree with their noun phrase as -a, -aj, -an, -ajn, whether they precede or follow the noun; predicate adjectives agree with the subject after esti. Use A-words rather than bare English-style noun modifiers, track phrase boundaries rather than nearest nouns, and distinguish adjective ellipsis such as la ruĝan from an independent O-word such as ruĝon.
Related Topics
- Adjective Agreement in NumberA1 — Learn why Esperanto adjectives take -j when they describe plural people or things, in both noun phrases and predicates.
- Adjective Agreement in the AccusativeA1 — Learn when Esperanto adjectives copy the accusative -n, how -ajn is built, and why predicative adjectives normally remain without -n.
- Attributive and Predicative AdjectivesA2 — Distinguish adjectives inside noun phrases from adjectives that assert a subject's or object's state, and choose agreement endings accordingly.
- Adjective PositionA2 — Learn the neutral and marked positions of Esperanto adjectives, and use word order to control emphasis, clarity, and scope.
- Substantivized AdjectivesA1 — Distinguish adjectives used with an omitted noun from true nouns formed from the same root, and mark number and case correctly in both patterns.
- Nouns and the -O EndingA1 — Build Esperanto nouns with -o, then add -j for plural and -n for accusative while respecting meaning and countability.