Greek nouns and adjectives end in vowels whose sound underdetermines their spelling. The /o/ at the end of a word can be ο or ω; the /i/ can be η or ι. Sounding the word out is useless — ο and ω are pronounced identically, as are η and ι. But the endings are not random. Each grammatical slot — a particular gender, in a particular case — has one fixed vowel letter. Once you can name a form ("this is a genitive plural", "this is a neuter singular"), the spelling is already decided for you. This page gives you that decision procedure.
The letter comes from the grammar, not the sound
The governing idea, exactly as with verb endings: identify the word's part of speech, gender, and case, and the vowel follows automatically. Here is the master table for the common endings:
| Slot | Ending | Letter | Example |
|---|---|---|---|
| Masculine nominative sg | -ος | omicron | ο δρόμος (the road) |
| Neuter nominative/accusative sg | -ο | omicron | το δώρο (the gift) |
| Neuter nom/acc sg | -ι | iota | το παιδί (the child) |
| Feminine nominative sg | -η / -ή | eta | η αγάπη (love) |
| Genitive plural (all genders) | -ων | omega | των ανθρώπων (of the people) |
| Adverb from -ος adjective | -ως | omega | ακριβώς (exactly) |
Read that table as a set of promises. If a word is a genitive plural, the ending will be -ων with omega — every time, no exceptions. If it is a neuter singular in /o/, it will be -ο with omicron. The vowel is a function of the grammar.
Masculine -ος and neuter -ο: both omicron
The /o/ that ends a masculine noun (-ος) or a neuter noun (-ο) is omicron. This is the default /o/ spelling for the base form of a word.
Ο δρόμος για το χωριό είναι κλειστός σήμερα.
o dhrómos ya to chorió íne klistós símera.
The road to the village is closed today.
Πήρα ένα μικρό δώρο για τη μαμά μου.
píra éna mikró dhóro ya ti mamá mu.
I got a small gift for my mom.
Note that -ος can also close a neuter noun (το μέρος "place", το λάθος "mistake", το δάσος "forest") — it is still omicron. Gender changes which words take -ος, but never the vowel letter.
The genitive plural: always -ων (omega)
This is the single most reliable rule on the page. Every genitive plural, in every gender, ends in -ων with omega. Masculine, feminine, neuter — all collapse to the same -ων in the "of the ..." plural.
Η γλώσσα των νέων αλλάζει συνέχεια.
i ghlósa ton néon alázi sinéchia.
The language of young people is always changing.
Ο δάσκαλος των παιδιών είναι πολύ αυστηρός.
o dháskalos ton pedhión íne polí afstirós.
The children's teacher is very strict.
Τα δικαιώματα των εργαζομένων πρέπει να προστατεύονται.
ta dhikeómata ton erghazoménon prépi na prostatévonde.
Workers' rights must be protected.
Compare this with the genitive singular of a masculine noun, which ends in -ου (omicron+upsilon, the /u/ sound): του ανθρώπου, του δρόμου. So the pattern across the two "of" forms is: singular -ου (omicron), plural -ων (omega). Never mix them.
Adverbs in -ως take omega
A very common way to build an adverb from a -ος adjective is the ending -ως, which is spelled with omega: ακριβώς (exactly), βεβαίως (of course), αμέσως (at once), τελείως (completely), κυρίως (mainly), ευτυχώς (fortunately).
Ήρθε ακριβώς στην ώρα του, ούτε λεπτό αργότερα.
írthe akrivós stin óra tu, úte leptó arghótera.
He came exactly on time, not a minute later.
Ευτυχώς είχαμε πάρει ομπρέλα μαζί μας.
eftichós íchame pári obréla mazí mas.
Fortunately we had brought an umbrella with us.
The καλός / καλώς trap
Now the two /o/ endings collide. The adjective "good" is καλός (omicron); the adverb/interjection "well, all right" is καλώς (omega). They are pronounced identically — kalós — but they are different words, and the vowel letter is the only thing that shows which one you mean. καλώς lives above all in the standard welcome καλώς όρισες / καλώς ήρθες ("welcome").
Είναι πολύ καλός άνθρωπος, θα σου αρέσει.
íne polí kalós ánthropos, tha su arési.
He's a very good person, you'll like him.
Καλώς ήρθατε στην Ελλάδα!
kalós írthate stin eládha!
Welcome to Greece!
Feminine -η vs neuter -ι
The /i/ ending divides the same way. A feminine noun in /i/ takes -η (or stressed -ή): η αγάπη, η νίκη, η τέχνη, η αδερφή, η ψυχή. A neuter noun in /i/ takes -ι: το παιδί, το ψωμί, το σπίτι, το κρασί, το χέρι. Gender predicts the letter.
Το παιδί τρώει ψωμί με μέλι στην κουζίνα.
to pedhí trói psomí me méli stin kuzína.
The child is eating bread with honey in the kitchen.
Η αγάπη δεν έχει ηλικία.
i aghápi dhen échi ilikía.
Love has no age.
Η αδερφή μου σπουδάζει στη Θεσσαλονίκη.
i adherfí mu spudházi sti thesaloníki.
My sister studies in Thessaloniki.
The definite article is your safety check: το always precedes a neuter (το παιδί, so the ending is -ι), η always precedes a feminine (η αγάπη, so the ending is -η). Fix the article and the vowel follows.
Common Mistakes
1. Writing a neuter singular with omega. A neuter noun in /o/ ends in -ο (omicron).
❌ Πήρα ένα ωραίο δώρω για τα γενέθλιά της.
Wrong — a neuter noun ends in -ο (omicron): δώρο. Omega is for genitive plurals and adverbs.
✅ Πήρα ένα ωραίο δώρο για τα γενέθλιά της.
píra éna oréo dhóro ya ta yenéthliá tis.
I got a nice gift for her birthday.
2. Spelling the genitive plural with omicron. It is always -ων (omega).
❌ Η ζωή των ανθρώπον έχει αλλάξει πολύ.
Wrong — the genitive plural always ends in -ων (omega): των ανθρώπων.
✅ Η ζωή των ανθρώπων έχει αλλάξει πολύ.
i zoí ton anthrópon échi aláksi polí.
People's lives have changed a lot.
3. Confusing the adjective καλός with the adverb καλώς. Describing a noun → omicron.
❌ Είναι ένας καλώς φίλος.
Wrong — the adjective 'good' is καλός (omicron); καλώς is the adverb 'well'.
✅ Είναι ένας καλός φίλος.
íne énas kalós fílos.
He's a good friend.
4. Giving a neuter noun the feminine -η. A neuter in /i/ takes -ι (iota).
❌ Το παιδή κοιμάται ήδη.
Wrong — a neuter noun in /i/ takes -ι: το παιδί (-η is a feminine ending).
✅ Το παιδί κοιμάται ήδη.
to pedhí kimáte ídhi.
The child is already asleep.
5. Giving a feminine noun the neuter -ι. A feminine in /i/ takes -η (eta).
❌ Η αγάπι της μητέρας είναι ανιδιοτελής.
Wrong — the feminine noun ends in -η: η αγάπη.
✅ Η αγάπη της μητέρας είναι ανιδιοτελής.
i aghápi tis mitéras íne anidhiotelís.
A mother's love is selfless.
Key Takeaways
- The closing vowel is chosen by gender and case, not by sound. Name the form and the letter is fixed.
- Omicron: masculine -ος (δρόμος) and neuter -ο (δώρο). Omega: genitive plural -ων (των ανθρώπων) and adverbs -ως (ακριβώς).
- The genitive plural is always -ων (omega) in every gender — the most reliable rule here. Contrast the masculine genitive singular -ου (omicron).
- η vs ι: feminine nouns take -η (αγάπη), neuter nouns take -ι (παιδί); let the article (η / το) tell you which.
- Watch καλός (adjective, omicron) vs καλώς (adverb/greeting, omega).
Now practice Greek
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Start learning Greek→Related Topics
- The Three GendersA1 — Every Greek noun is masculine, feminine, or neuter — and that gender, shown by its article ο / η / το, controls the adjectives and pronouns around it, so you learn each noun together with its article, not on its own.
- Spelling the /i/ Sound: η ι υ ει οιA2 — The single hardest thing about writing Greek: five different spellings — η, ι, υ, ει, οι (plus archaic υι) — all sound identical, /i/. You can't hear which one a word takes, but you can predict most of them from grammatical endings and word families. This is the page to master.
- Spelling the /o/ Sound: ο vs ωA2 — Two letters, ο (omicron) and ω (omega), spell the identical sound /o/. Which one you write is mostly decided by the grammatical ending — verbs end -ω, neuter nouns -ο, masculines -ος — and getting it wrong can flip a verb into a noun: καλώ ('I invite') vs καλό ('good').