κατά is unusual because it belongs to two case patterns. With the accusative, it most often means “during,” “around,” or “according to”; with the genitive, it means “against.” Much of its accusative use is (formal) or preserved in fixed expressions, but phrases such as κατά λάθος and κατά τη γνώμη μου are entirely normal in everyday conversation. For the wider genitive inventory, see genitive after learned prepositions.
The case carries the contrast
| Construction | Core meaning | Register | Model |
|---|---|---|---|
| κατά + accusative | during; around; according to; by | fixed everyday phrases or (formal) prose | κατά τη διάρκεια · κατά τις πέντε |
| κατά + genitive | against, opposed to | (formal); journalistic and institutional | κατά της πρότασης |
| κατά without an object | against | everyday in voting and debate | Είμαι κατά. |
The distinction is visible most clearly in the article: κατά τον κανονισμό has an accusative phrase and means “under the regulation,” whereas κατά του κανονισμού has a genitive phrase and means “against the regulation.” English word order gives no comparable signal, so learn the case as part of the meaning.
Κατά τον κανονισμό, η δοκιμή θα διαρκέσει έξι μήνες.
katá ton kanonizmó, i dhokimí tha dhiarkési éksi mínes
Under the regulation, the trial will last six months. (formal)
Η αντιπολίτευση ψήφισε κατά της πρότασης.
i adipolítefsi psífise katá tis prótasis
The opposition voted against the proposal. (formal / journalistic)
Time: during and approximately
For an event seen as a span, κατά + accusative means “during.” The very common expression κατά τη διάρκεια + genitive literally means “during the duration of.” It is neutral in careful writing and common in announcements; casual speech often prefers όταν “when” or ενώ “while.”
Κατά τη διάρκεια της πτήσης δεν επιτρέπεται το κάπνισμα.
katá ti dhiárkia tis ptísis dhen epitrépete to kápnizma
Smoking is not permitted during the flight. (formal announcement)
Κατά τη συζήτηση προέκυψαν δύο σοβαρά προβλήματα.
katá ti sizítisi proékipsan dhío sovará provlímata
Two serious problems arose during the discussion. (formal)
Before a clock time, κατά + accusative means “around, approximately”: κατά τις πέντε. It deliberately makes the time less exact than στις πέντε “at five.”
Θα περάσω κατά τις πέντε, αλλά θα σου στείλω μήνυμα πριν φύγω.
tha peráso katá tis pénde, alá tha su stílo mínima prin fígho
I'll come by around five, but I'll message you before I leave.
Viewpoint, authority, and orientation
κατά + accusative can present a viewpoint, rule, source, or standard. Some combinations are everyday fixed phrases; others are (formal) or (academic) and are best learned as complete units.
Κατά τη γνώμη μου, πρέπει να το συζητήσουμε ξανά.
katá ti ghnómi mu, prépi na to sizitísume ksaná
In my opinion, we need to discuss it again.
Κατά τον νόμο, ο εργοδότης οφείλει να απαντήσει γραπτώς.
katá ton nómo, o erghodhótis ofíli na apandísi ghraptós
Under the law, the employer must reply in writing. (formal / legal)
Direction toward something also occurs with the accusative, but it is less usual in everyday Standard Greek and often (literary); ordinary speech normally uses προς or σε instead.
Το παλιό μπαλκόνι βλέπει κατά τη θάλασσα.
to palió balkóni vlépi katá ti thálasa
The old balcony faces toward the sea. (literary)
This directional use is a real construction, not a productive prefix rule. Words beginning in κατα-, such as κατεβαίνω and καταγράφω, are lexical compounds with their own histories and meanings; they are not phrases containing the preposition κατά.
Opposition: κατά + genitive
When κατά points at the target of opposition, accusation, or hostile action, it takes the genitive and belongs mainly to (formal), journalistic, legal, and political language. Everyday speech often uses ενάντια σε + accusative. With no expressed object, υπέρ ή κατά; “for or against?” and είμαι κατά are ordinary.
Οι κάτοικοι κατέθεσαν προσφυγή κατά της απόφασης.
i kátiki katéthesan prosfighí katá tis apófasis
The residents filed an appeal against the decision. (formal / legal)
Δεν είμαι κατά, αλλά θέλω να ξέρω πόσο θα κοστίσει.
dhen íme katá, alá thélo na kséro póso tha kostísi
I'm not against it, but I want to know how much it will cost.
Fixed phrases worth learning whole
The accusative survives in many adverb-like phrases. Their meaning is conventional, so changing the noun or case freely does not create a new phrase.
| Phrase | Meaning | Register |
|---|---|---|
| κατά λάθος | by mistake | everyday |
| κατά κύριο λόγο | mainly, primarily | neutral; frequent in (formal) prose |
| κατά συνέπεια | consequently | (formal) |
| κατά τη γνώμη μου | in my opinion | everyday |
Σου έστειλα κατά λάθος το παλιό αρχείο.
su éstila katá láthos to palió archío
I sent you the old file by mistake.
Η καθυστέρηση οφείλεται κατά κύριο λόγο στην κακοκαιρία.
i kathistérisi ofílete katá kírio lógho stin kakokería
The delay is mainly due to the bad weather. (formal)
Δεν υποβλήθηκαν τα απαραίτητα έγγραφα και, κατά συνέπεια, η αίτηση απορρίφθηκε.
dhen ipovlíthikan ta aparétita éngrafa ke, katá sinépia, i étisi aporífthike
The required documents were not submitted and, consequently, the application was rejected. (formal)
Common Mistakes
❌ Ψήφισαν κατά την πρότασης.
Incorrect — the article is accusative but πρότασης is genitive; 'against the proposal' requires a fully genitive phrase.
✅ Ψήφισαν κατά της πρότασης.
psífisan katá tis prótasis
They voted against the proposal. (formal)
❌ Κατά της διάρκεια της συνάντησης δεν μίλησε κανείς.
Incorrect — 'during' takes κατά + accusative: κατά τη διάρκεια.
✅ Κατά τη διάρκεια της συνάντησης δεν μίλησε κανείς.
katá ti dhiárkia tis sinándisis dhen mílise kanís
No one spoke during the meeting. (formal)
❌ Κατά λάθους κατέβηκα σε λάθος στάση.
Incorrect — κατά λάθος is a fixed accusative expression.
✅ Κατά λάθος κατέβηκα σε λάθος στάση.
katá láthos katévika se láthos stási
I got off at the wrong stop by mistake.
Key Takeaways
- κατά + accusative expresses time, approximation, viewpoint, standard, manner, or direction; many uses are fixed or (formal).
- κατά + genitive means “against” and is common in institutional language; objectless είμαι κατά is everyday.
- Memorize κατά λάθος, κατά τη γνώμη μου, κατά κύριο λόγο, κατά συνέπεια as whole expressions.
Related Topics
- Genitive After Learned PrepositionsB1 — The closed set of formal prepositions — εναντίον, υπέρ, λόγω, μεταξύ, εντός, εκτός, μέσω, αντί, πλην, διά — that take the genitive instead of the accusative, why they all come from the written language, what the everyday σε-alternatives are, and the one place where a preposition can swallow a weak pronoun.
- Prepositional IdiomsC1 — Ten fixed Greek prepositional phrases for everyday, emphatic, and formal meanings that cannot be assembled word by word.
- Temporal Prepositions and TimeA2 — How Greek expresses at, before, after, during, within, for, and from–to time spans—and when it uses no preposition at all.
- Accusative for Time and DurationA2 — Greek often says την Κυριακή, το πρωί, δύο ώρες and τρεις φορές την εβδομάδα with a bare accusative where English uses on, in, for or per — and this page maps the neutral bare patterns against meaningful σε and για alternatives.