English gets away with one word — that — for two completely different jobs. "I know that he left" reports a fact; "I want that you leave" (or rather "I want you to leave") points at something that hasn't happened yet and may never. Greek refuses to blur these. It uses ότι / πως for the first job and να for the second, and picking the wrong one is one of the most persistent B1 errors. The good news is that the split is not a list to memorise — it follows a single, teachable idea.
The one idea: fact vs non-fact
ότι and πως introduce a reported fact — a piece of reality that you are stating, claiming, or passing on. The verb inside stays fully indicative (present, past, future — whatever the tense of the actual event).
να introduces a non-fact — a wish, an aim, a request, an order, a possibility, or any event that is merely envisaged rather than asserted. The verb inside is the subjunctive form (bare να + conjugated verb), because you are not saying it happened; you are saying it is wanted, feared, or possible.
Λέει ότι ήρθε νωρίς χθες το βράδυ.
léi óti írthe norís chthes to vrádhi
He says (that) he came early last night.
Ξέρω πως είναι εδώ, είδα το αμάξι του κάτω.
kséro pos íne edhó, ídha to amáksi tu káto
I know (that) he's here — I saw his car downstairs.
Θέλω να έρθει κι αυτός, θα χαρεί πολύ.
thélo na érthi ki aftós, tha charí polí
I want him to come too — he'll be really pleased.
In the first two, the coming and the being-here are presented as things that are true. In the third, the coming is only wanted — it exists in my head, not (yet) in the world. That is the whole distinction, and once it clicks you can predict the complementizer for verbs you have never met.
Which verbs take which
You rarely have to reason it out sentence by sentence, because the main verb tells you which world you are in.
| Take ότι / πως (report a fact) | Take να (aim at a non-fact) |
|---|---|
| λέω (say), δηλώνω (state) | θέλω (want), επιθυμώ (wish) |
| ξέρω (know), μαθαίνω (learn/find out) | ζητάω (ask), παρακαλώ (beg) |
| νομίζω (think), πιστεύω (believe) | λέω σε κάποιον (tell someone to) |
| βλέπω (see), ακούω (hear) | αφήνω (let), βάζω (get someone to) |
| καταλαβαίνω (understand) | πρέπει (must), μπορεί (may) |
The left column is verbs of saying, thinking, knowing, and perceiving — all of them handle information about what is the case. The right column is verbs of wanting, asking, ordering, permitting, and causing — all of them reach toward something not yet real. A quick test: if you could paraphrase your clause with "the fact that…", you want ότι/πως; if you could paraphrase it with "…to do it" or "…that it should happen," you want να.
Μου είπε ότι δεν θα προλάβει να έρθει στο πάρτι.
mu ípe óti dhen tha prolávi na érthi sto párti
She told me (that) she won't make it to the party.
Νομίζω πως έχει δίκιο, αλλά δεν είμαι σίγουρος.
nomízo pos échi dhíkio, alá dhen íme síghuros
I think (that) he's right, but I'm not sure.
Της ζήτησα να μου κρατήσει μια θέση μπροστά.
tis zítisa na mu kratísi mia thési brostá
I asked her to save me a seat at the front.
Notice the first example nests both: ότι reports the fact (she told me that), and inside it να carries the un-happened event (make it to come). They coexist happily — each is doing its own job.
The same verb, two meanings
A handful of high-frequency verbs sit on the fence and accept either complementizer — and the choice flips the meaning. This is where the fact/non-fact logic really earns its keep.
The clearest case is λέω. With ότι it means "say (that) — report"; with να it means "say to — propose / tell someone to."
Λέει ότι φεύγει αύριο το πρωί.
léi óti févyi ávrio to proí
He says (that) he's leaving tomorrow morning. (a report)
Λέει να πάμε σινεμά απόψε, έχει μια καλή ταινία.
léi na páme sinemá apópse, échi mia kalí tenía
He's suggesting we go to the cinema tonight — there's a good film on. (a proposal)
Both are perfectly correct Greek — but they are different sentences. The first passes on information; the second floats a plan. Nothing but the complementizer tells them apart.
The same fork opens with ξέρω: with ότι it means "know that (a fact)"; with να it means "know how to (an ability)."
Ξέρω ότι οδηγείς καλά, μη μου το λες συνέχεια.
kséro óti odhiyís kalá, mi mu to les sinéchia
I know (that) you drive well — stop telling me all the time.
Ξέρω να οδηγώ μηχανή, αλλά μου λείπει το δίπλωμα.
kséro na odhighó michaní, alá mu lípi to dhíploma
I know how to ride a motorbike, but I don't have the licence.
ότι and πως are interchangeable — but mind the accent
When they mean "that," ότι and πως are true synonyms. Swap one for the other freely; ότι is a touch more neutral in writing, πως a touch more colloquial, but nothing rides on the choice.
Κατάλαβα ότι κάτι δεν πήγαινε καλά.
katálava óti káti dhen píyene kalá
I realised (that) something wasn't right.
Κατάλαβα πως κάτι δεν πήγαινε καλά.
katálava pos káti dhen píyene kalá
I realised (that) something wasn't right. (same meaning)
The one trap is spelling. The complementizer πως ("that") is written without an accent. Its lookalike πώς — with the accent (tonos) on the ω — is the interrogative "how?" These are two different words that happen to share four letters, and putting the accent on the "that" version is a real spelling mistake, not a stylistic choice.
Ξέρω πως δεν φταις εσύ γι' αυτό.
kséro pos dhen ftes esí yi aftó
I know (that) it's not your fault.
Ρώτησε πώς πάει η δουλειά στο καινούριο γραφείο.
rótise pos pái i dhuliá sto kenúrio ghrafío
She asked how work is going at the new office.
Common Mistakes
1. Putting ότι after θέλω. English "I want that…" tempts you toward ότι, but wanting reaches at a non-fact, so Greek demands να.
❌ Θέλω ότι μου τηλεφωνήσεις το βράδυ.
Incorrect — θέλω (wanting) governs a non-fact, so it takes να, never ότι.
✅ Θέλω να μου τηλεφωνήσεις το βράδυ.
thélo na mu tilefonísis to vrádhi
I want you to call me in the evening.
2. Putting ότι after πρέπει. Obligation and possibility (πρέπει, μπορεί) are non-facts by nature — they run on να.
❌ Πρέπει ότι φύγουμε τώρα, αργήσαμε.
Incorrect — πρέπει (obligation) takes να, not ότι.
✅ Πρέπει να φύγουμε τώρα, αργήσαμε.
prépi na fíghume tóra, aryísame
We have to leave now, we're late.
3. Accenting the complementizer πως. The "that" word has no accent; the accent belongs only to the interrogative πώς ("how").
❌ Νομίζω πώς έχεις δίκιο.
Incorrect — the 'that' complementizer is πως, unaccented; πώς with the accent means 'how'.
✅ Νομίζω πως έχεις δίκιο.
nomízo pos échis dhíkio
I think (that) you're right.
4. Using ότι after a causative verb. Making, letting, or getting someone to do something is causing a non-fact, so βάζω, αφήνω and their kin take να.
❌ Τον έβαλα ότι πλύνει τα πιάτα.
Incorrect — 'get someone to do X' is causation, which requires να.
✅ Τον έβαλα να πλύνει τα πιάτα.
ton évala na plíni ta piáta
I got him to wash the dishes.
Key Takeaways
- ότι / πως = a reported fact (indicative inside); να = a non-fact — wish, request, order, possibility (subjunctive inside).
- The main verb decides: saying / thinking / knowing / perceiving → ότι/πως; wanting / asking / ordering / causing / πρέπει / μπορεί → να.
- Some verbs take both with a meaning shift: λέω ότι (report) vs λέω να (propose); ξέρω ότι (know a fact) vs ξέρω να (know how to).
- ότι = πως in meaning, but write the complementizer πως without an accent — πώς means "how?"
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Start learning Greek →Related Topics
- να After Emotion and EvaluationB1 — Verbs and expressions of feeling and judgement — μου αρέσει να, φοβάμαι να, χαίρομαι, λυπάμαι, αξίζει, είναι κρίμα — take a να-clause for the event itself and που for the real fact that stirs the feeling; how to tell which one you need.