Many persistent Greek errors are not failures of vocabulary or conjugation. They arise because two forms are both genuine Greek, but only one expresses the viewpoint, clause type, participant role, or register intended in that context. English may translate both with the same word—or use one construction where Greek maintains a contrast.
This page is a route map, not sixteen condensed lessons. Start with the question you are trying to answer, follow the matching guide, and return here when a different “which one?” problem appears.
Complete decision map
| Decision | Use this route when... |
|---|---|
| να vs θα | you are choosing between a projected, desired, deliberated action and a future/probability statement |
| Imperfect vs Aorist | you need a one-screen route between an internal/open past viewpoint and a bounded presentation |
| πού/που, πώς/πως, πότε/ποτέ | you need to distinguish accented interrogatives from unaccented relative or complementizer uses |
| ότι vs ό,τι | you are spelling complementizer “that” versus free-relative “whatever” |
| πρέπει vs χρειάζεται | you are separating obligation from practical need, especially under negation |
| ξέρω vs γνωρίζω | you need everyday “know,” formal acquaintance, or the event “meet/get to know” |
| ξέρω να vs μπορώ να | English “can” might mean learned skill, present ability, possibility, or permission |
| μου αρέσει vs αγαπάω | you are choosing experiencer “like” versus transitive, stronger “love” |
| λέω vs μιλάω | you are distinguishing said content from the activity of speaking or talking |
| ας vs να | you need a compact choice among suggestion, deliberation, permission, and concession |
| πιο + adjective vs -τερος | you know the two comparison patterns but need the safer form for an adjective or register |
| για + noun vs για να + verb | English “for” might introduce a noun, topic, recipient, or purpose event |
| να vs ότι/πως | the complement is an asserted/reported proposition or a desired, possible, requested prospect |
| Perfect vs Aorist | you are choosing present relevance/experience versus a bounded past occasion |
| δεν vs μη(ν) | you need the negator for an indicative claim versus a subjunctive, prohibition, purpose, warning, or fear frame |
| σε vs από | you are mapping location/goal against origin/source, unless lexical government decides |
The four guides in the final rows live with their grammatical owners, where the necessary depth already exists. They appear here so that the learner sees one complete decision map without the explanations being duplicated.
Recurring logic 1: assertion versus prospect
Greek often distinguishes an event presented as a proposition from one merely projected, desired, required, or deliberated. This motivates both ότι/πως vs να and part of θα vs να. “Fact versus wish” is a useful first approximation, but ότι does not guarantee objective truth: it can introduce a claim the speaker doubts. The precise contrast is how the clause is being presented.
Η Μαρία λέει ότι θα μείνει ως το Σάββατο.
i María léi óti tha míni os to Sávato.
Maria says that she will stay until Saturday. (reported proposition)
Η Μαρία θέλει να μείνει ως το Σάββατο.
i María théli na míni os to Sávato.
Maria wants to stay until Saturday. (desired prospect)
In a first-person question, θα may ask what is expected to happen, while να asks what course of action to choose.
Θα φύγω μόλις τελειώσει η συνεδρίαση;
tha fígho mólis teliósi i sinedhríasi;
Will I leave as soon as the meeting ends?
Να φύγω μόλις τελειώσει η συνεδρίαση;
na fígho mólis teliósi i sinedhríasi;
Should I leave as soon as the meeting ends?
The dedicated routes cover modal probability, intentions, complements, and verbs that change meaning with the clause type.
Recurring logic 2: bounded versus internal/open viewpoint
Greek past aspect does not label situations as objectively “completed” or “ongoing.” The speaker packages a situation either as a bounded occurrence or finite series (aorist) or from inside its development, state, habit, or background frame (imperfect). A single event can be presented internally, and a repeated series can be packaged as bounded.
Διάβαζα την αναφορά όταν χτύπησε το κουδούνι.
dhiávaza tin anaforá ótan chtípise to kudhúni.
I was reading the report when the doorbell rang. (internal background plus bounded interruption)
Διάβασα την αναφορά δύο φορές πριν απαντήσω.
dhiávasa tin anaforá dhío forés prin apandíso.
I read the report twice before replying. (finite repeated series viewed as bounded)
Duration, event count, and adverbs are evidence supplied by context, not mechanical tense switches. The Imperfect vs Aorist flowchart routes each branch into the full aspect guide.
Recurring logic 3: clause frame selects negation
“Statement versus command” captures the most visible contrast between δεν and μη(ν), but the real distribution is broader. Δεν negates indicative claims; μη(ν) occupies subjunctive, prohibition, purpose, warning, and related non-indicative frames.
Δεν ανοίγουμε το παράθυρο επειδή έχει θόρυβο έξω.
dhen aníghume to paráthiro epidhí échi thórivo ékso.
We aren't opening the window because it's noisy outside. (indicative statement)
Να μην ανοίξουμε το παράθυρο όσο κοιμάται το μωρό.
na min aníksume to paráthiro óso kimáte to moró.
Let's not open the window while the baby is sleeping. (subjunctive proposal)
This is why English not cannot choose the Greek particle by itself. Read the clause frame around the verb.
Recurring logic 4: selection versus open classification
The contrast between ποιος and τι is sometimes summarized as “identity versus category,” but that is not absolute. Ποιος often selects a person or item from a relevant set and agrees with an expressed or understood noun. Invariable τι asks more openly for what something is and also appears in fixed expressions. Overlap depends on discourse and the implied noun; the full guide is τι vs ποιος.
Ποιο είναι το δικό σου σακίδιο;
pio íne to dhikó su sakídhio;
Which one is your backpack? (selection from a set)
Τι είναι αυτό το εξάρτημα;
ti íne aftó to eksártima;
What is this component? (open classification)
Common Mistakes
Treating aspect as objective event type
One occurrence is not automatically aorist, and repetition is not automatically imperfect. Viewpoint decides.
Εκείνη τη στιγμή έτρεχα μόνος μου στο πάρκο.
ekíni ti stighmí étrecha mónos mu sto párko.
At that moment I was running alone in the park. (one event viewed internally)
Τρεις Κυριακές στη σειρά έτρεξα δέκα χιλιόμετρα.
tris Kiriakés sti sirá étreksa dhéka chiliómetra.
For three Sundays in a row I ran ten kilometers. (delimited repeated series viewed as bounded)
Assuming ότι guarantees that a claim is true
It marks a reported or asserted proposition, including one the current speaker rejects.
Ισχυρίζεται ότι πλήρωσε, αλλά η απόδειξη δείχνει το αντίθετο.
ischirízete óti plírose, alá i apódhiksi dhíchni to antítheto.
He claims that he paid, but the receipt shows the opposite.
Putting ότι after a verb of wanting
Wanting projects an event instead of asserting it.
❌ Θέλω ότι έρθεις λίγο νωρίτερα αύριο.
Incorrect — θέλω takes a projected να-clause.
✅ Θέλω να έρθεις λίγο νωρίτερα αύριο.
thélo na érthis lígho norítera ávrio.
I want you to come a little earlier tomorrow.
Mixing the indicative and subjunctive negator slots
The sequence is να + μη(ν), with the final ν selected by the following sound.
❌ Να δεν αργήσεις στην αυριανή συνάντηση.
Incorrect — a να-clause takes μη(ν), not δεν.
✅ Να μην αργήσεις στην αυριανή συνάντηση.
na min aryísis stin avrianí sinándisi.
Don't be late for tomorrow's meeting.
Key Takeaways
- A “choosing” error usually involves two real forms whose distribution differs from English.
- Use the routing table first; the destination page owns the rule, edge cases, and practice.
- Past aspect is bounded viewpoint versus internal/open viewpoint, not an objective completed/ongoing classification.
- Assertion/prospect, clause frame, participant role, selection, and register are recurring decision dimensions.
- Treat concise labels as diagnostics, then test the actual context rather than applying them as absolutes.
Related Topics
- να vs ότι/πως (that-Clauses)B1 — The core complementizer split — ότι and πως report something that IS the case, while να points at something wished-for, aimed-at, or merely possible — and how the same verb (λέω, ξέρω) can take either one with a change of meaning.
- Imperfect vs AoristB1 — Use one compact decision flow to choose an internal or open past viewpoint versus an occurrence or finite series packaged as bounded.
- δεν vs μη(ν)A2 — Choose δεν for indicative facts and μη(ν) inside command, subjunctive, purpose, warning, and fear frames.