Imperfect Past

Romanisation follows today's pronunciation, with the stressed vowel marked: th = θ as in "think", dh = δ as in "this", ch = χ as in Scottish "loch", gh = γ (y before e and i sounds).

The imperfect (παρατατικός, paratatikós) is the past of actions seen as ongoing or repeated: "I was reading", "we used to go", "she kept calling". It is built on the present stem, and it pairs with the aorist the way "was doing" pairs with "did" in English.

Group A: present stem + endings

Person	Ending	γράφω → έγραφα	διαβάζω → διάβαζα
εγώ	-α	έγραφα	διάβαζα
εσύ	-ες	έγραφες	διάβαζες
αυτός, αυτή, αυτό	-ε	έγραφε	διάβαζε
εμείς	-αμε	γράφαμε	διαβάζαμε
εσείς	-ατε	γράφατε	διαβάζατε
αυτοί, αυτές, αυτά	-αν(ε)	έγραφαν	διάβαζαν

The endings are those of the aorist, and so is the stress rule: the stress falls on the third syllable from the end, and short verbs take a stressed έ- only in the forms that need it (έγραφα, but γράφαμε). Compare the two pasts of γράφω: imperfect έγραφα (I was writing, I used to write) and aorist έγραψα (I wrote).

Group B: -ούσα

Group B verbs take -ούσα: μιλάω → μιλούσα, μιλούσες, μιλούσε, μιλούσαμε, μιλούσατε, μιλούσαν; μπορώ → μπορούσα. The stress stays on -ού-, so no augment appears.

Imperfect or aorist?

Imperfect: ongoing, repeated, background	Aorist: single, completed
Κάθε καλοκαίρι πηγαίναμε στη Νάξο. - Every summer we used to go to Naxos.	Πέρσι πήγαμε στη Νάξο. - Last year we went to Naxos.
Διάβαζα όταν... - I was reading when...	...χτύπησε το τηλέφωνο. - ...the phone rang.
Ο παππούς μου έλεγε ιστορίες. - My grandfather used to tell stories.	Μου είπε μια ιστορία. - He told me a story.

The question to ask is not "how long?" but "is it seen as a whole or as in progress?". Δούλευα δέκα χρόνια στην Αθήνα and Δούλεψα δέκα χρόνια στην Αθήνα are both possible: the first describes those years as a period of your life, the second sums them up as a finished stretch.

For English speakers

English marks the difference with "was -ing" and "used to"; Greek marks it on the verb stem, and you must choose one every time you talk about the past. Time words help: κάθε μέρα, συχνά, πάντα suggest the imperfect; χθες, μια φορά, ξαφνικά suggest the aorist.

• *εδιαβάζαμε → διαβάζαμε.
• *εμιλούσα → μιλούσα (the stress is on -ού-, so there is no έ-).
• "I used to swim every day" is Κάθε μέρα κολυμπούσα; κολύμπησα would sum up a finished stretch of days.
• "I was writing when you came" is Έγραφα όταν ήρθες; Έγραψα όταν ήρθες means "I wrote (it) when you came".