In short

A Greek adjective is never a fixed word. It copies three things from the noun it describes: gender, number and case. English says a good friend, good friends, I see the good friend with one unchanging form; Greek says ο καλός φίλος, οι καλοί φίλοι, βλέπω τον καλό φίλο. The largest and most regular family ends in -ος (masculine), -η (feminine), -ο (neuter): καλός, καλή, καλό. After a vowel the feminine is -α instead: ωραίος, ωραία, ωραίο. Agreement holds both inside the noun phrase (το ωραίο σπίτι) and after είμαι (Το σπίτι είναι ωραίο).

The rule

1. Three genders, one adjective. Every adjective has a full set of forms. You choose the one that matches the noun:

• masculine noun → masculine adjective: ο μεγάλος κήπος
• feminine noun → feminine adjective: η μεγάλη πόλη
• neuter noun → neuter adjective: το μεγάλο σπίτι

The noun decides. Nothing about the meaning of big changes; only the ending does.

2. Number and case travel with gender. Agreement is not just gender. If the noun is plural, the adjective is plural; if the noun is in the accusative, the adjective is in the accusative too. In practice this means the article, the adjective and the noun move together as a block:

Notice that all three words change at once. A useful check: the adjective usually rhymes with the article — ο…ός, τον…ό, οι…οί, τους…ούς.

3. Two positions, same agreement.

• Attributive — the adjective stands between the article and the noun: ο νέος δάσκαλος, τα μεγάλα παιδιά, βλέπω την ωραία θάλασσα.
• Predicative — the adjective stands after είμαι (or a similar verb) and has no article of its own: Ο δάσκαλος είναι νέος. Τα παιδιά είναι μεγάλα. Η θάλασσα είναι ωραία.

The predicative adjective still agrees, and after είμαι it is in the nominative, because it describes the subject.

4. The -ος / -α / -ο subtype. When the ending -ος follows a vowel, the feminine is -α, not -η:

• ωραίος → ωραία (after ι)
• νέος → νέα (after ε)
• πλούσιος → πλούσια (after ι)
• άδειος → άδεια (after ι)

The masculine and neuter are unaffected: ωραίος / ωραίο, νέος / νέο. The plurals are identical to the -η type, the feminine included — the ending is -ες either way: ωραίες, νέες.

5. Beware μικρός. The letter ρ is a consonant, so it does not bring the -α feminine with it: μικρός → μικρή, not *μικρά in the singular, and likewise καθαρός → καθαρή. The same goes for every other consonant stem here: ακριβός → ακριβή, κακός → κακή, εύκολος → εύκολη. Only the four listed above (ωραίος, νέος, πλούσιος, άδειος) take -α here.

6. Stress does not move. In this adjective class the accent stays on the same syllable throughout the paradigm: εύκολος, εύκολη, εύκολο, εύκολοι, εύκολες, εύκολα — always on the ευ. Likewise καλός, καλή, καλό, καλοί, καλές, καλά — always on the ending.

Forms & patterns

καλός, καλή, καλό — the -ος / -η / -ο type

Singular:

Plural:

The bare endings, without the article:

ωραίος, ωραία, ωραίο — the -ος / -α / -ο subtype (after a vowel)

Singular:

Plural:

Only the feminine singular differs from the καλός type (-α instead of -η). Everything else is the same.

The adjective with its noun — a full noun phrase

μεγάλος + κήπος (masc.), μεγάλη + πόλη (fem.), μεγάλο + παιδί (neut.):

The eight adjectives of this lesson

And two more of the -α subtype, for practice:

Examples

Common mistakes

• ο καλός φίλος, η καλός φίλη -> ο καλός φίλος, η καλή φίλη — the adjective must change gender with the noun; it is not a fixed word.
• το σπίτι είναι μεγάλος -> το σπίτι είναι μεγάλο — after είμαι the adjective still agrees, here with the neuter subject το σπίτι.
• βλέπω τον καλός φίλο -> βλέπω τον καλό φίλο — an accusative noun takes an accusative adjective; τον καλός mixes two cases.
• η ωραίη θάλασσα -> η ωραία θάλασσα — after a vowel (ωραί-) the feminine ending is -α, not -η.
• η μικρά πόλη -> η μικρή πόλη — μικρός is a plain -η adjective; do not extend the -α rule to it.
• τα παιδιά είναι μεγάλες -> τα παιδιά είναι μεγάλα — neuter plural is -α; -ες is feminine.
• οι καλές φίλοι -> οι καλοί φίλοι — masculine plural nominative is -οι; -ες belongs to the feminine.
• βλέπω τους μεγάλοι κήπους -> βλέπω τους μεγάλους κήπους — masculine plural accusative is -ους, matching the article τους.

Tips

• Learn every new adjective as a trio: καλός, καλή, καλό. Learning only the masculine leaves you guessing at two thirds of the word.
• Use the rhyme check: in the masculine, article and adjective end alike — ο…ός, τον…ό, οι…οί, τους…ούς. If they clash, one of them is wrong.
• The neuter is the lazy gender: -ο in the singular, -α in the plural, and the nominative and accusative are identical. Το ωραίο σπίτι — βλέπω το ωραίο σπίτι.
• To decide between -η and -α in the feminine, look at the letter just before -ος: a vowel (ωραί-ος, νέ-ος, πλούσι-ος, άδει-ος) gives -α; a consonant (καλ-ός, μικρ-ός, εύκολ-ος) gives -η.
• After είμαι the adjective is in the nominative and takes no article: Η δουλειά είναι εύκολη — not *η εύκολη.
• When one adjective describes two nouns of different gender, use the neuter plural for things and the masculine plural for people: Το βιβλίο και η εφημερίδα είναι καινούρια. Ο Γιάννης και η Μαρία είναι καλοί.
• Practise by taking one noun phrase through the four boxes: ο μεγάλος κήπος → τον μεγάλο κήπο → οι μεγάλοι κήποι → τους μεγάλους κήπους. Four forms, one meaning.