In short

English builds its verb system out of tenses; Greek builds it out of two stems. Nearly every Greek verb keeps a continuous stem (εξακολουθητικό θέμα, as in γράφ-ω) and a simple stem (συνοπτικό θέμα, as in γράψ-ω). The choice between them is called το ποιόν ενέργειας, and it is not about when something happens but about how you frame it: as one bounded, complete act, or as something ongoing, repeated or habitual.

This is the single most important decision in Greek verb morphology, because almost every tense and mood you will meet from now on is just one of these two stems plus a small marker. Learn each new verb as a pair, the way you learn a noun with its article.

The rule

1. Two stems, one verb. γράφω and γράψω are not two verbs and not two tenses. They are the same verb seen through two lenses:

• εξακολουθητικό (continuous) — γράφ-, διαβάζ-, δουλεύ-: the action stretches, repeats, or is presented as a habit or a general truth.
• συνοπτικό (simple / perfective) — γράψ-, διαβάσ-, δουλέψ-: the action is taken as a single whole event, one complete occurrence, with no interest in its inner duration.

2. The simple stem never stands alone. This is the rule that saves beginners the most trouble. A form built on the συνοπτικό stem — γράψω, διαβάσεις, πάρουμε, δουν — is never a sentence by itself. It only ever appears after a small word that licenses it:

Because it always depends on such a word, this form is called η εξαρτημένη (the dependent) in modern reference grammars; older school grammars file it under η υποτακτική. If nothing licenses it, use the continuous stem.

3. The present tense has no perfective. You cannot present something as one closed event while it is still going on in front of you, so the present is always built on the εξακολουθητικό stem: γράφω “I write / I am writing / I do write”. Greek makes no separate progressive form at all — one present covers all three English translations.

4. The triggers allow the perfective, they do not force it. After θα, να, όταν and the rest, both stems are possible, and the meaning changes: θα γράψω “I’ll write (one letter, once)” against θα γράφω “I’ll be writing / I’ll write regularly”. This is the aspect contrast in its purest form.

5. είμαι and έχω have no contrast. These two verbs carry only one stem, so θα είμαι, να είμαι, θα έχω, να έχω are simply the forms — nothing to choose. Do not invent *να είμω or *να έχσω.

Forms & patterns

Recognition table: high-frequency pairs (1st person singular)

Learn every verb in this shape from now on.

The first four are regular and predictable; the last five are unpredictable - some fetch their second stem from another root, others reshape the root they have. Lesson 23 explains where each column comes from.

γράφω — both stems, all six persons

The endings are identical; only the stem changes.

μιλάω — a second-conjugation verb

Note that the perfective column of a second-conjugation verb behaves exactly like γράψω: the two conjugations of lesson 6 differ only in the continuous column.

The four irregular dependents you need first

These are short and very frequent; the monosyllables carry no accent.

πάω is special: the same short forms serve as an everyday continuous present as well (πάω στη δουλειά “I’m going to work”), while πηγαίνω is the fuller continuous form.

The contrast at a glance

Examples

Common mistakes

• Γράψω τώρα. -> Γράφω τώρα. — A perfective form can never head a clause on its own; with nothing to license it, only the continuous stem is possible.
• Δεν διαβάσω αυτό το βιβλίο. -> Δεν διαβάζω αυτό το βιβλίο. — δεν is a negator, not a trigger. To negate a perfective you still need θα or να: δεν θα το διαβάσω, να μην το διαβάσω.
• Θα είδα την ταινία αύριο. -> Θα δω την ταινία αύριο. — The simple stem is not a past tense. δω, πω, φάω point at nothing in time by themselves; θα + simple stem is the ordinary future.
• Θα γράψω κάθε μέρα. -> Θα γράφω κάθε μέρα. — κάθε μέρα is repetition, so the future has to be built on the continuous stem.
• Θέλω να πίνω έναν καφέ τώρα. -> Θέλω να πιω έναν καφέ τώρα. — One single act needs the simple stem. The continuous stem is not the equivalent of English “-ing”: it covers habits too, and it excludes one-off complete events.
• Συνήθως θα πάρω το λεωφορείο. -> Συνήθως παίρνω το λεωφορείο. — A habitual statement about the present takes the plain continuous present, with no θα at all.
• Θέλω να είμω εκεί στις πέντε. -> Θέλω να είμαι εκεί στις πέντε. — είμαι has no second stem; the same form serves both aspects. The same goes for έχω.
• Μόλις τρώω, θα σε πάρω τηλέφωνο. -> Μόλις φάω, θα σε πάρω τηλέφωνο. — “As soon as I’ve eaten” is one completed event, so μόλις here licenses the simple stem.

Tips

• Store every new verb as a pair in your notes — γράφω / γράψω, παίρνω / πάρω — and drill the second column out loud after να. A verb learned in one column only is half learned.
• Before you choose, ask two questions in this order: is there a trigger word (θα, να, ας, αν, όταν, μόλις)? If no, the continuous stem is your only option. If yes, then ask: one whole event, or ongoing/repeated?
• Words like κάθε μέρα, πάντα, συνήθως, συνέχεια pull towards the continuous stem; μια φορά, αμέσως, γρήγορα, τελικά pull towards the simple one.
• Do not translate the English progressive. “I am reading” and “I read” are both διαβάζω; the extra dimension Greek adds is not duration but completeness.
• The simple stem is the gateway form: once you can produce γράψω, you already hold the key to the future (lesson 24), the subjunctive (lesson 25), the imperative (lesson 26) and, with a small change, the past (lesson 32).
• Aspect is a choice, not a rule handed down by the sentence. Both θα σου γράφω and θα σου γράψω are correct Greek; they simply promise different things.
• When you genuinely cannot decide, the continuous stem is the safer guess in a bare clause and the simple stem is the safer guess after να and θα with a one-off action.