In short

The imperfect (ο παρατατικός) is built the easy way: take the continuous stem — the one you already use for the present — and add the same past endings you learned for the aorist: -α, -ες, -ε, -αμε, -ατε, -αν. Nothing else changes. γράφω gives έγραφα “I was writing, I used to write”, διαβάζω gives διάβαζα, and the verb είμαι has its own set, ήμουν, ήσουν, ήταν.

Second-conjugation verbs in -άω/-ώ and -ώ/-είς do not attach those endings directly. They insert -ούσ- first: μιλώ gives μιλούσα, αγαπώ gives αγαπούσα, μπορώ gives μπορούσα. So there are really only two shapes to learn — the plain one and the -ούσα one.

The rule

1. One stem, one ending set. The aorist used the simple (perfective) stem: έγραψα. The imperfect uses the continuous (imperfective) stem: έγραφα. The endings are literally identical in both tenses; the stem alone carries the difference. If you can say έγραψα, you already know how to finish έγραφα.

2. The augment appears only when it is stressed. Exactly as in lesson 32, the past tense wants its stress on the third syllable from the end. When the stem is too short to provide one, a syllabic augment ε- is added to carry it: έ-γρα-φα, έ-γρα-φες, έ-γρα-φε, έ-γρα-φαν. In the first and second person plural the longer ending -αμε / -ατε already pushes the stress back onto the stem, so the augment is dropped: γράφαμε, γράφατε — never έγραφαμε.

3. Long stems never take an augment at all. A stem of two or more syllables can host the stress by itself, so no ε- is needed anywhere in the paradigm: διαβάζω → διάβαζα, δουλεύω → δούλευα, περιμένω → περίμενα. Note that the stress moves back one syllable compared with the present (διαβάζω → διάβαζα).

4. Second conjugation: the -ούσ- infix. Verbs stressed on the ending in the present (μιλάω/μιλώ, αγαπάω/αγαπώ, οδηγώ, μπορώ, ζω, τηλεφωνώ) form the imperfect with -ούσα, -ούσες, -ούσε, -ούσαμε, -ούσατε, -ούσαν. The stress sits on -ού- throughout, so no augment is ever involved.

5. What the imperfect means. Three everyday jobs:

• Ongoing background — an action seen from inside, without an end point: χθες έβρεχε “it was raining yesterday”, τι έκανες όταν σε πήρα τηλέφωνο;
• Habit or repetition in the past — with κάθε μέρα, πάντα, συνήθως, τότε: κάθε μέρα διάβαζα δύο ώρες “every day I used to study two hours”.
• Politeness. ήθελα and θα μπορούσα soften a request into something less blunt than the present: ήθελα έναν καφέ, παρακαλώ “I’d like a coffee, please”; θα μπορούσατε να μου δείξετε τον δρόμο; “could you show me the way?” With μπορώ the polite version keeps θα in front; the bare imperfect μπορούσατε να… only asks whether you were able to at the time. Here nothing past is meant at all — the distance in tense is simply distance in tone.

Choosing between the imperfect and the aorist in a longer narrative is a topic of its own; lesson 43 handles it. For now, take the imperfect where English says “was/were -ing” or “used to”.

Forms & patterns

The past endings (the same set as the aorist)

First conjugation, short stem: γράφω → έγραφα

First conjugation, long stem: διαβάζω → διάβαζα (no augment anywhere)

Second conjugation: μιλάω / μιλώ → μιλούσα

The same pattern gives αγαπούσα (αγαπώ), οδηγούσα (οδηγώ), μπορούσα (μπορώ), ζούσα (ζω), τηλεφωνούσα (τηλεφωνώ), ρωτούσα (ρωτάω).

είμαι → ήμουν (its own paradigm; learn it whole)

Frequent irregular and stem-changing imperfects

είχα is the only one that keeps its stress on the same syllable in every person, so it needs no augment and shows no gap between singular and plural.

Examples

Common mistakes

• γραφούσα -> έγραφα — the -ούσ- infix belongs to the second conjugation only; a verb stressed on the stem in the present (γράφω, not γραφώ) never takes it.
• διαβαζούσα -> διάβαζα — same trap with a longer first-conjugation verb; the length of the stem changes nothing.
• έγραφαμε -> γράφαμε — the augment exists only to carry the stress, and -αμε has already moved the stress onto the stem, so ε- must go.
• έτρωγαμε -> τρώγαμε — the rule is mechanical and applies to irregulars too: no augment in the εμείς and εσείς forms.
• έγραφσα / γράφησα -> έγραφα — do not paste the aorist’s -σ- onto the continuous stem; the endings are already identical, and the stem alone marks the tense.
• Κάθε βράδυ μίλησα με τη μητέρα μου. -> Κάθε βράδυ μιλούσα με τη μητέρα μου. — a repeated habit needs the continuous stem, not the aorist one.
• ήμουνα, ήσουνα, ήτανε, είχανε, λέγανε -> ήμουν, ήσουν, ήταν, είχαν, έλεγαν — these longer variants are common in relaxed speech and dictionaries do record them, but the -ε / -α tail belongs to the spoken register; keep the short forms in anything you write.

Tips

• Test for the augment out loud: count three syllables back from the end. If your finger lands outside the word, you need ε-; if it lands on the stem, you do not.
• Learn each first-conjugation verb as a pair of shapes — έγραφα / γράφαμε — rather than as six separate cells. The other four follow from those two.
• If the present is stressed on the last syllable (μιλώ, αγαπώ, μπορώ), the imperfect is -ούσα. That single question sorts almost every verb correctly.
• In speech you will also hear μίλαγα, αγάπαγα, ρώταγα alongside μιλούσα, αγαπούσα, ρωτούσα. Recognise them, but write the -ούσα forms.
• ήθελα and θα μπορούσα are your everyday politeness tools in a shop, an office or a hotel — they are softer than θέλω and μπορείτε without being formal.
• Time expressions do half the work for you: with κάθε μέρα, πάντα, συνήθως, τότε, όλη μέρα the imperfect is nearly always the form you want.
• Watch the second accent when a weak pronoun follows a word stressed three syllables from the end: ο δάσκαλός μου μιλούσε, το αυτοκίνητό μας ήταν παλιό.