If you learn one adjective paradigm, make it this one. The -ος / -η / -ο class is the largest and most regular in Greek — καλός (good), μικρός (small), μεγάλος (big), ψηλός (tall), όμορφος (beautiful), ακριβός (expensive), φθηνός (cheap) and thousands more belong to it. And it comes with a gift: you do not have to memorise three new sets of endings, because each gender declines like a noun you already know. Master this table and you can inflect most of the adjectives in the language.
The shortcut: three familiar declensions
Look at what the three genders are built from:
- The masculine in -ος declines exactly like the masculine noun ο δρόμος — see masculine nouns in -ος.
- The feminine in -η declines like a feminine noun in -η (η αγάπη, η νίκη).
- The neuter in -ο declines like the neuter noun το βουνό.
So the adjective is not a fourth thing to learn — it is three things you have already met, wearing the same stem. Here is καλός in full.
The singular
| Case | Masculine | Feminine | Neuter |
|---|---|---|---|
| Nominative | καλός | καλή | καλό |
| Genitive | καλού | καλής | καλού |
| Accusative | καλό | καλή | καλό |
| Vocative | καλέ | καλή | καλό |
The plural
| Case | Masculine | Feminine | Neuter |
|---|---|---|---|
| Nominative | καλοί | καλές | καλά |
| Genitive | καλών | καλών | καλών |
| Accusative | καλούς | καλές | καλά |
| Vocative | καλοί | καλές | καλά |
Four things are worth pointing out, because they are the patterns that repeat across the whole class:
- The -ς shows up in only two masculine cells: the nominative singular (καλός) and the accusative plural (καλούς). Everywhere else the masculine has no final -ς.
- The feminine keeps -η in the nominative and accusative singular (καλή / καλή) — it never changes there.
- The neuter matches the masculine in the genitive (καλού) and, of course, is the same in nominative and accusative (καλό / καλό), like every neuter.
- The genitive plural is καλών for all three genders. It is the one cell where the three columns collapse into a single form.
Ο Νίκος είναι σπάνια καλός φίλος, πάντα εκεί όταν τον χρειάζεσαι.
o Níkos íne spánia kalós fílos, pánda ekí ótan ton chriázese
Nikos is a rare kind of good friend — always there when you need him.
Η καλή μας γειτόνισσα μάς κρατάει τα κλειδιά όταν λείπουμε.
i kalí mas yitónisa mas kratái ta klidhiá ótan lípume
Our good neighbour keeps our keys when we're away.
Πήραμε ένα πολύ καλό κρασί για το τραπέζι της Κυριακής.
pírame éna polí kaló krasí ya to trapézi tis Kiriakís
We got a really good wine for Sunday lunch.
Η γνώμη ενός καλού φίλου αξίζει περισσότερο από χίλιες συμβουλές.
i ghnómi enós kalú fílu aksízi perisótero apó chílies simvulés
A good friend's opinion is worth more than a thousand pieces of advice.
Across all three genders in context
The whole point of the paradigm is that the same adjective reshapes itself for whatever noun it lands on. Watch μικρός and ακριβός move through genders and numbers:
Ψάχνω ένα μικρό διαμέρισμα, όχι πολύ ακριβό, κοντά στη σχολή.
psáchno éna mikró dhiamérizma, óchi polí akrivó, kondá sti scholí
I'm looking for a small flat, not too expensive, near the college.
Οι καλοί μαθητές δεν είναι πάντα οι πιο έξυπνοι, είναι οι πιο επίμονοι.
i kalí mathités dhen íne pánda i pio éksipni, íne i pio epímoni
The good students aren't always the cleverest — they're the most persistent.
Έχω λίγους αλλά καλούς φίλους, και μου φτάνει.
écho líghus alá kalús fílus, ke mu ftáni
I've got few but good friends, and that's enough for me.
Ελπίζω να μας έχεις μόνο καλά νέα σήμερα.
elpízo na mas échis móno kalá néa símera
I hope you've only got good news for us today.
The vocative in -ε
When you address someone, the masculine singular takes -ε, exactly like the masculine -ος noun (φίλος → φίλε). The whole phrase goes vocative together — article dropped, adjective and noun both in the vocative:
Καλέ μου φίλε, χάθηκες τελείως τον τελευταίο καιρό!
kalé mu fíle, cháthikes telíos ton teleftéo keró
My good friend, you've completely vanished lately!
The feminine and neuter vocatives are just the same as their nominatives (καλή, καλό), so the only special vocative form to remember is the masculine -ε.
Accent: fixed, unlike the matching nouns
Here is one genuinely useful difference from the noun page. The endings above are the whole story — but you also need to know where the stress sits, and this is where adjectives behave better than nouns. The masculine noun ο άνθρωπος shifts its accent forward in the genitive (του ανθρώπου); the corresponding kind of adjective does not. An adjective stressed on the third-from-last syllable, like όμορφος, keeps that accent through the entire paradigm in the modern standard:
Θαύμασα για ώρα τη θέα του όμορφου κόλπου από ψηλά.
thávmasa ya óra ti théa tu ómorfu kólpu apó psilá
I gazed for ages at the view of the beautiful bay from up high.
Του όμορφου — the accent stays on ό, where the matching noun would have pushed it forward. Oxytone adjectives (καλός, μικρός, ψηλός, ακριβός) glue their accent to the ending and never move it either. So for this class you can treat the accent as stable and just swap endings. The handful of formal exceptions that do shift, and the full reasoning, are on accent in adjective declension; the parallel noun rule that these adjectives quietly opt out of is on accent shift in declension.
The sibling class: -ος / -α / -ο
Not every -ος adjective takes an -η feminine. When a vowel comes right before the ending, the feminine is -α instead: νέος / νέα / νέο (new, young), ωραίος / ωραία / ωραίο (nice), παλιός / παλιά / παλιό (old). Everything else — the masculine, the neuter, the whole plural — is identical to the class on this page; only the feminine singular differs. That variant is worked out on adjectives in -ος / -α / -ο; this page covers the -η feminine, which is the larger group.
Αγόρασαν ένα ωραίο παλιό σπίτι σε ένα χωριό της Πελοποννήσου.
aghórasan éna oréo palió spíti se éna chorió tis Peloponísu
They bought a lovely old house in a village in the Peloponnese.
Common Mistakes
1. Giving the feminine an -α ending when it should be -η. For a consonant-stem adjective like καλός, the feminine is καλή, not ×καλά (which is the adverb "well").
❌ Μου ήρθε μια καλά ιδέα στον δρόμο.
Incorrect — the feminine of καλός is καλή: μια καλή ιδέα.
✅ Μου ήρθε μια καλή ιδέα στον δρόμο για τη δουλειά.
mu írthe mia kalí idhéa ston dhrómo ya ti dhuliá
A good idea came to me on the way to work.
2. Using -οι for the neuter plural. The neuter plural of this class is -α, and -οι is the masculine.
❌ Τα μικροί παιδιά κουράστηκαν στη διαδρομή.
Incorrect — the neuter plural is -α: τα μικρά παιδιά.
✅ Τα μικρά παιδιά κουράστηκαν στη διαδρομή και αποκοιμήθηκαν.
ta mikrá pedhiá kurástikan sti dhiadhromí ke apokimíthikan
The little kids got tired on the journey and fell asleep.
3. Leaving the masculine plural in -οι when it is an object. The accusative plural is -ούς.
❌ Κάλεσα όλους τους καλοί μου φίλους στα γενέθλια.
Incorrect — as an object the adjective is accusative plural: τους καλούς μου φίλους.
✅ Κάλεσα όλους τους καλούς μου φίλους στα γενέθλιά μου.
kálesa ólus tus kalús mu fílus sta yenéthliá mu
I invited all my good friends to my birthday.
4. Not putting the adjective in the genitive. In a genitive phrase the adjective is genitive too.
❌ Η τιμή του φθηνός εισιτηρίου ανέβηκε ξαφνικά.
Incorrect — the adjective is genitive: του φθηνού εισιτηρίου.
✅ Η τιμή του φθηνού εισιτηρίου ανέβηκε ξαφνικά μέσα σε μια νύχτα.
i timí tu fthinú isitiríu anévike ksafniká mésa se mia níchta
The price of the cheap ticket suddenly went up overnight.
5. Using the nominative form to address someone. The masculine vocative is -ε.
❌ Καλός μου φίλε, σε ευχαριστώ για όλα.
Incorrect — the vocative is καλέ: Καλέ μου φίλε.
✅ Καλέ μου φίλε, σε ευχαριστώ για όλα όσα έκανες.
kalé mu fíle, se efcharistó ya óla ósa ékanes
My good friend, thank you for everything you did.
Key Takeaways
- The -ος / -η / -ο class is the biggest and most regular adjective type — καλός, μικρός, μεγάλος, όμορφος, ακριβός, φθηνός.
- Each gender copies a noun declension you already know: masculine like ο δρόμος, feminine like η αγάπη, neuter like το βουνό.
- The -ς appears only in the masculine nominative singular (καλός) and accusative plural (καλούς); the genitive plural is καλών for all three genders.
- The masculine vocative is -ε (καλέ); the feminine and neuter vocatives copy their nominatives.
- Unlike the matching -ος nouns, these adjectives keep their accent fixed through the paradigm (του όμορφου, not ×του ομόρφου).
- When a vowel precedes the ending the feminine is -α (νέος → νέα): that sibling class is on adjectives in -ος / -α / -ο.
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Start learning Greek →Related Topics
- Adjectives in -ος / -α / -οA2 — The vowel-stem variant of the -ος adjective — ωραίος/ωραία/ωραίο, νέος/νέα/νέο, κρύος/κρύα/κρύο — where the feminine ends in -α (not -η) and lands on the same spelling as the neuter plural.
- Masculine Nouns in -οςA1 — The largest masculine class — nouns like ο δρόμος, ο ουρανός and ο άνθρωπος — with its full singular and plural paradigm, the accent shift that hits antepenult-stressed nouns in the genitive, and the -ε vocative.
- Accent in Adjective DeclensionB2 — Where the stress sits as an adjective declines — and the good news that, unlike nouns, the everyday -ος/-η/-ο adjective keeps its accent fixed (όμορφος → του όμορφου, not ×του ομόρφου). The oxytone and -ύς classes, the learned -ής/-ές genitives that carry the stress, and the handful of formal doublets (του άγιου vs του Αγίου).