Aorists of Vowel-Stem Verbs | Greek Grammar

Most Greek aorists are built by adding the perfective -σα to a stem that ends in a consonant, which is why they merge into -ψα, -ξα or -σα. But a handful of everyday verbs have a stem that ends in a vowel — ακούω ("hear"), κλαίω ("cry"), καίω ("burn"), φταίω ("be at fault"). With no consonant to merge into, you would expect them all to add a plain -σα. One of them does exactly that. The others spring a small surprise, and the surprise has a tidy historical reason worth knowing, because it turns three "irregular" forms into one predictable pattern.

The clean type: ακούω → άκουσα

ακούω is the model of a well-behaved vowel-stem verb. The stem is ακου-, ending in the vowel sound -u-, and the aorist simply bolts -σα straight onto it: άκουσα. Nothing merges, nothing changes.

Person	Form	Reading
εγώ	άκουσα	ákusa
εσύ	άκουσες	ákuses
αυτός/-ή/-ό	άκουσε	ákuse
εμείς	ακούσαμε	akúsame
εσείς	ακούσατε	akúsate
αυτοί/-ές/-ά	άκουσαν	ákusan

The accent behaves exactly as it does in any aorist: it falls as far back as the three-syllable rule allows. In the singular and 3rd plural that is the initial ά- of the stem (άκουσα — here the stem-initial α carries it, not a separate augment), while the longer 1st/2nd-plural endings pull it one syllable forward (ακούσαμε, ακούσατε). Nothing here is special to vowel-stems — it is the ordinary recessive aorist accent.

Άκουσα κάτι να πέφτει στην κουζίνα και τρόμαξα.

ákusa káti na péfti stin kuzína ke trómaksa

I heard something fall in the kitchen and got startled.

Δεν άκουσες το ξυπνητήρι σου σήμερα το πρωί;

dhen ákuses to ksipnitíri su símera to proí;

Didn't you hear your alarm this morning?

Ακούσαμε τις ειδήσεις στο ραδιόφωνο του αυτοκινήτου.

akúsame tis idhísis sto radhiófono tu aftokinítu

We heard the news on the car radio.

The -αίω verbs: a consonant hiding in the diphthong

Now the surprise. Three common verbs end in -αίω — κλαίω (cry), καίω (burn), φταίω (be to blame) — and instead of a plain -σα they give -ψα or -ξα:

Present	→ Aorist	Meaning
κλαίω	έκλαψα	cry
καίω	έκαψα	burn
φταίω	έφταιξα	be at fault, be to blame

Why -ψα and -ξα, when there is no π/β/φ or κ/γ/χ in sight? Because there used to be. Historically these stems ended in a consonant that the modern spelling has swallowed into the diphthong: κλαίω comes from an old κλαυ- (a labial u), so κλαυ- + σα → κλαψα; likewise καίω from καυ- → καψα; φταίω is a slightly different case: Ancient πταίω already had a plain σ-aorist (ἔπταισα), and the modern -ξ- in έφταιξα is an analogy — φταίω simply behaves like a velar stem and gives -ξα, so you can treat it the same way. In other words the -αίω verbs are best handled as consonant-stems in disguise, merging for the very same reason any labial or velar merges: -ψ- is just [ps], -ξ- is just [ks], with the σ already baked in. Once you know the hidden consonant, the "irregularity" evaporates.

Το μωρό έκλαψε όλη νύχτα και δεν κλείσαμε μάτι.

to moró éklapse óli níchta ke dhen klísame máti

The baby cried all night and we didn't sleep a wink.

Έκλαψα από τη χαρά μου όταν την είδα στο αεροδρόμιο.

éklapsa apó ti chará mu ótan tin ídha sto aerodhrómio

I cried for joy when I saw her at the airport.

Πρόσεχε, έκαψα κατά λάθος το ρύζι στην κατσαρόλα.

prósiche, ékapsa katá láthos to rízi stin katsaróla

Careful, I accidentally burned the rice in the pot.

Εγώ έφταιξα για τον καβγά, το παραδέχομαι.

eghó éfteksa ya ton kavghá, to paradhéchome

I was to blame for the argument, I admit it.

Ποιος έφταιξε που χάλασε όλο το σχέδιο;

pios éftekse pu chálase ólo to schédhio;

Whose fault was it that the whole plan fell apart?

💡

Don't guess a plain -σα for these. There is no ×έκλαισα, ×έκαισα or ×έφταισα — the buried consonant always wins, giving έκλαψα, έκαψα, έφταιξα. Learn the three as a little rhyming set and you will never regularize them.

The suppletive vowel-stems belong to another page

Two of the most frequent vowel-final verbs of all — λέω (say) and τρώω (eat), together with πάω (go) — also end in a vowel, but they do not merge anything: they switch to a completely different root. λέω → είπα, τρώω → έφαγα, πάω → πήγα. These are pure suppletion, not vowel-stem merging, so they live with the irregular and suppletive aorists. It is worth keeping the two ideas apart: άκουσα / έκλαψα are regular outcomes of a vowel (or hidden-consonant) stem, while είπα / έφαγα are root swaps you memorise wholesale.

Είπα καληνύχτα σε όλους και πήγα για ύπνο.

ípa kaliníchta se ólus ke pígha ya ípno

I said goodnight to everyone and went to bed.

Common Mistakes

1. Regularizing κλαίω to a plain -σα. The hidden labial makes it -ψα.

❌ Το παιδί έκλαισε γιατί έχασε το παιχνίδι του.

Incorrect — κλαίω hides a labial: the aorist is έκλαψε.

✅ Το παιδί έκλαψε γιατί έχασε το παιχνίδι του.

to pedhí éklapse yatí échase to pechnídhi tu

The child cried because it lost its toy.

2. Regularizing φταίω. The hidden velar makes it -ξα, not -σα.

❌ Δεν έφταισα εγώ που αργήσαμε τόσο πολύ.

Incorrect — φταίω hides a velar: the aorist is έφταιξα.

✅ Δεν έφταιξα εγώ που αργήσαμε τόσο πολύ.

dhen éfteksa eghó pu aryísame tóso polí

It wasn't my fault that we were so late.

3. Adding a merge consonant to ακούω. A true vowel-stem takes a plain -σα, with no ξ or ψ.

❌ Άκουξα ότι παντρεύεται τον άλλο μήνα.

Incorrect — ακούω is a clean vowel-stem: the aorist is άκουσα.

✅ Άκουσα ότι παντρεύεται τον άλλο μήνα.

ákusa óti pandrévete ton álo mína

I heard she's getting married next month.

4. Not shifting the accent to the stem in the plural. As in every aorist, the long ending pulls it forward: ακούσαμε.

❌ Άκουσαμε τη μουσική από το διπλανό διαμέρισμα.

Incorrect — the 1st plural moves the accent forward: ακούσαμε.

✅ Ακούσαμε τη μουσική από το διπλανό διαμέρισμα.

akúsame ti musikí apó to dhiplanó dhiamérizma

We heard the music from the flat next door.

Key Takeaways

Vowel-stem verbs add the perfective -σα with no consonant to merge — the clean case is ακούω → άκουσα.
The -αίω trio hides an old consonant and merges anyway: κλαίω → έκλαψα and καίω → έκαψα (buried labial → -ψα), φταίω → έφταιξα (behaves like a velar stem → -ξα). There is no plain -σα form.
The accent follows the normal aorist pattern: άκουσα in the singular, ακούσαμε in the 1st/2nd plural.
Keep these apart from the suppletive vowel-finals λέω → είπα, τρώω → έφαγα, πάω → πήγα, which switch root entirely — see the irregular and suppletive aorists.
All four verbs — hear, cry, burn, be-at-fault — are everyday vocabulary, so their aorists earn their keep fast.

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