αυ and ευ: av/af, ev/ef | Greek Grammar

Two of the most useful words a beginner learns — αύριο ("tomorrow") and ευχαριστώ ("thank you") — both hide the same surprise. The pairs αυ and ευ are not simple vowels. Each is a vowel (α or ε) followed by a consonant sound that is written with υ but pronounced as either [v] or [f]. Which one you get depends entirely on the sound that comes next. English speakers almost universally get this wrong on first contact, so it is worth nailing early.

αυ and ευ are vowel + [v]/[f], never a diphthong

The trap is the letter υ. Elsewhere it can be a vowel [i], but inside αυ and ευ the υ turns into a consonant — [v] or [f]. So:

αυ = "av" or "af"
ευ = "ev" or "ef"

They are never the English "ow" of cow, the "aw" of saw, or the "you"/"ew" of few. If you find yourself saying "ow-tos" for αυτός or "you-ropi" for Ευρώπη, reset: there is a [v] or [f] in there.

The voicing rule: look at the next sound

The choice between [v] and [f] follows a single, fully predictable rule based on the following sound — the same voiced/voiceless split you met with the "th" letters:

Followed by…	αυ	ευ	Because the next sound is…
a vowel or a voiced consonant (β, γ, δ, ζ, λ, μ, ν, ρ)	av [av]	ev [ev]	voiced → the υ stays voiced [v]
a voiceless consonant (θ, κ, ξ, π, σ, τ, φ, χ, ψ) or the end of the word	af [af]	ef [ef]	voiceless → the υ devoices to [f]

The logic is assimilation: the υ-consonant simply matches the voicing of whatever follows it. Before a buzzing sound it buzzes ([v]); before a breathy sound (or silence at the word's end) it goes breathy ([f]). You don't have to memorise word lists — you read the next letter and the rule decides.

αυ = av (before voiced) / af (before voiceless)

Θα σε δω αύριο το πρωί.

tha se dho ávrio to proí

I'll see you tomorrow morning.

Θέλω ένα βραστό αυγό.

thélo éna vrastó avghó

I'd like a boiled egg.

In αύριο the next sound is ρ (voiced) → "áv-rio"; in αυγό it's γ (voiced) → "av-ghó". Now flip to voiceless:

Αυτός είναι ο αδερφός μου.

aftós íne o adherfós mu

This is my brother.

Το αυτοκίνητο δεν ξεκινάει.

to aftokínito dhen ksekinái

The car won't start.

Here αυ is followed by τ (voiceless) → "af": aftós, aftokínito. Same two letters αυ, opposite consonant, because the following sound flipped from voiced ρ/γ to voiceless τ.

💡

αυτός — "this / he", one of the commonest words in Greek — is af-TÓS, not "ow-tos". The τ that follows is voiceless, so the υ becomes [f]. Lock this word in and you've internalised the whole rule.

ευ = ev (before voiced) / ef (before voiceless)

Η Ευρώπη έχει πάρα πολλές γλώσσες.

i evrópi échi pára polés ghlóses

Europe has a great many languages.

Είναι πολύ ευγενικός μαζί μου.

íne polí evyenikós mazí mu

He's very kind to me.

Ευρώπη → ρ is voiced → "ev-rópi"; ευγενικός → γ is voiced → "ev-yenikós". And the voiceless side:

Ευχαριστώ πολύ για τη βοήθεια.

efcharistó polí ya ti voíthia

Thank you very much for the help.

Μη χάσεις αυτή την ευκαιρία.

mi chásis aftí tin efkería

Don't miss this opportunity.

In ευχαριστώ the next sound is χ (voiceless) → "ef-charistó"; in ευκαιρία it's κ (voiceless) → "ef-kería". This is why the polite word you'll say fifty times a day is ef-charistó, never ev-charistó.

Before a voiceless consonant (and at a word's end): [f]

The devoicing happens whenever nothing voiced follows — before any voiceless consonant, and in the rare word that actually ends in αυ/ευ, where there is simply nothing to voice against. Everyday Greek has almost no word-final αυ/ευ, so the cleanest demonstration is a near-pair that turns entirely on the consonant right after αυ: ναύτης ("sailor"), where a voiceless τ follows and forces [f], versus Παύλος (Paul), where a voiced λ follows and keeps [v].

Ο παππούς μου ήταν ναύτης στο εμπορικό ναυτικό.

o papús mu ítan náftis sto emborikó naftikó

My grandfather was a sailor in the merchant navy.

Ο Παύλος μένει τώρα στη Θεσσαλονίκη.

o pávlos méni tóra sti thesaloníki

Pavlos now lives in Thessaloniki.

Contrast them directly: ναύτης has αυ before τ (voiceless) → "náf-tis", but Παύλος has αυ before λ (voiced) → "páv-los". The name and the noun differ only in what follows the αυ — and that's exactly what flips [f] to [v].

Why English speakers get this wrong

Two English instincts sabotage αυ and ευ. First, the diphthong reflex: in English, a vowel followed by u usually blends into a glide — au → "aw", eu → "you". Learners import that and read αυτός as "ow-tos", Ευρώπη as "you-ropi". Greek does no such blending; the υ is a full consonant. Second, once they discover the [v]/[f], learners tend to pick one and use it everywhere — usually [v], because υ "looks voiced". But the rule is contextual, and getting it backwards (saying "evcharistó" or "áfrio") sounds distinctly off to a native ear.

The remedy is a two-step habit: (1) there is a [v] or [f] hiding in every αυ/ευ — never a pure diphthong; (2) glance at the next sound to decide which. Voiced or vowel → v; voiceless or word-end → f.

Common Mistakes

1. Reading αυ as English "ow/aw". αυτός is "aftós", not "owtos".

❌ Αυτός είναι φίλος μου.

owtós íne fílos mu

Incorrect — αυ is never a diphthong; before τ it's [af], so 'aftós'.

✅ Αυτός είναι φίλος μου.

aftós íne fílos mu

This is my friend.

2. Reading ευ as English "you/ew". Ευρώπη is "Evrópi", not "You-ropi".

❌ Η Ευρώπη είναι μεγάλη.

i yurópi íne megháli

Incorrect — ευ hides a consonant; before ρ it's [ev], so 'Evrópi'.

✅ Η Ευρώπη είναι μεγάλη.

i evrópi íne megháli

Europe is big.

3. Using [v] before a voiceless sound. ευχαριστώ needs [f], because χ is voiceless.

❌ Ευχαριστώ πολύ.

evcharistó polí

Incorrect — χ is voiceless, so ευ devoices to [ef]: 'efcharistó'.

✅ Ευχαριστώ πολύ.

efcharistó polí

Thank you very much.

4. Using [f] before a voiced sound. αύριο needs [v], because ρ is voiced.

❌ Θα έρθω αύριο.

tha értho áfrio

Incorrect — ρ is voiced, so αυ stays [av]: 'ávrio'.

✅ Θα έρθω αύριο.

tha értho ávrio

I'll come tomorrow.

Key Takeaways

αυ = av / af and ευ = ev / ef — each is a vowel plus a hidden [v] or [f], never an English "ow" or "you".
[v]/[ev] before a vowel or a voiced consonant (β γ δ ζ λ μ ν ρ): αύριο, αυγό, Ευρώπη, ευγενικός.
[f]/[ef] before a voiceless consonant (θ κ ξ π σ τ φ χ ψ) or at the word's end: αυτός, αυτοκίνητο, ευχαριστώ, ευκαιρία, ναύτης.
The υ just assimilates to the next sound — read the following letter and the choice makes itself.
Anchor words: αυτός = "af-tós", ευχαριστώ = "ef-charistó", αύριο = "áv-rio".

Now practice Greek

Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.

Start learning Greek→