Two-way prepositions (in, an, auf, über, unter...)

You've already met prepositions that always take the accusative and ones that always take the dative — no matter what the sentence means. A third group is different: nine prepositions that can take either case, depending on whether the sentence describes a change of location or an existing location. These are called two-way prepositions (Wechselpräpositionen), and you actually already used one — in — this way back in basic prepositions of place and time.

Quick shortcut: ask wohin? (where to?) for a change of location — a new destination → accusative. Ask wo? (where?) for an existing location → dative. Same preposition, different question, different case.

The nine two-way prepositions

The test: wohin? vs wo?

Everything comes down to one question. Is the sentence describing a change of location — ending up somewhere new — or where something already is?

• Wohin gehst du? (Where are you going to?) → change of location → accusative
• Wo bist du? (Where are you?) → existing location → dative

Compare the same preposition in both roles:

• ✅ Ich gehe in den Park. (I'm going into the park.) — change of location, accusative
• ✅ Ich bin im Park. (I'm in the park.) — existing location, dative (in dem → im)
• ✅ Ich lege das Buch auf den Tisch. (I put the book onto the table.) — change of location, accusative
• ✅ Das Buch liegt auf dem Tisch. (The book is lying on the table.) — existing location, dative

Motion by itself isn't the test — what matters is whether the location itself changes. Ich gehe im Park spazieren (I'm going for a walk in the park) has plenty of movement, but it all happens within the same park — the location never changes, so it stays dative, not accusative.

The verb is still a useful clue, as long as you read it the same way: gehen (go), legen (put/lay), stellen (put/stand something up) usually describe reaching a new location — accusative. Sein (be), liegen (lie), stehen (stand) usually describe an existing location — dative. Hängen actually covers both roles, because German has two separate verbs that happen to be spelled the same: a transitive hängen — "hang something up" (hängte, hat gehängt) — that takes accusative, and an intransitive hängen — "be hanging" (hing, hat gehangen) — that takes dative: Ich hänge das Bild an die Wand (I hang the picture on the wall, accusative) vs. Das Bild hängt an der Wand (The picture is hanging on the wall, dative).

Working through all nine

• an — Ich stelle das Fahrrad an die Wand. (I put the bike against the wall.) / Das Fahrrad steht an der Wand. (The bike is against the wall.)
• auf — Die Katze springt auf den Tisch. (The cat jumps onto the table.) / Die Katze sitzt auf dem Tisch. (The cat is sitting on the table.)
• über — Der Vogel fliegt über die Brücke. (The bird flies over the bridge.) / Die Lampe hängt über dem Tisch. (The lamp is hanging over the table.)
• unter — Der Ball rollt unter das Auto. (The ball rolls under the car.) / Der Ball liegt unter dem Auto. (The ball is lying under the car.)
• vor — Sie stellt sich vor die Tür. (She steps in front of the door.) / Sie steht vor der Tür. (She's standing in front of the door.)
• hinter — Die Katze läuft hinter das Haus. (The cat runs behind the house.) / Die Katze ist hinter dem Haus. (The cat is behind the house.)
• neben — Er setzt sich neben mich. (He sits down next to me.) / Er sitzt neben mir. (He's sitting next to me.)
• zwischen — Sie stellt den Stuhl zwischen die Tische. (She puts the chair between the tables.) / Der Stuhl steht zwischen den Tischen. (The chair is standing between the tables.)

Remember: with a plural like die Tische in the dative (zwischen den Tischen), the noun itself also takes the -n ending you already know from the dative case.

Contractions

Just like in dem → im and in das → ins, several two-way prepositions contract when they combine with dem or das:

The contraction only exists for dem and das — feminine der and plural den never contract (an der Wand, not ❌ ander Wand).

Common mistakes

• ❌ Ich gehe in dem Park. → ✅ Ich gehe in den Park. (movement toward the park needs accusative, not dative)
• ❌ Ich bin in den Park. → ✅ Ich bin im Park. (already being there needs dative, not accusative)
• ❌ Das Buch liegt auf den Tisch. → ✅ Das Buch liegt auf dem Tisch. (liegen describes a fixed position — dative, even though English "lies on" can sound like an action)
• ❌ Er setzt sich neben ich. → ✅ Er setzt sich neben mich. (a pronoun after a two-way preposition follows the same accusative/dative choice as a noun would)

Quick check

Accusative or dative — and which form?

1. Ich hänge das Bild ____ (an) Wand. (movement — putting it up)
2. Das Bild hängt ____ (an) Wand. (already hanging there)
3. Die Kinder spielen ____ (unter) Baum. (fixed position, plural article needed? — no, singular tree)
4. Wir setzen uns ____ (zwischen) Fenster und Tür. (movement — sitting down there)

Key takeaways

• Nine prepositions switch between accusative and dative depending on meaning: an, auf, hinter, in, neben, über, unter, vor, zwischen.
• Ask wohin? (where to?) for a change of location → accusative. Ask wo? (where?) for an existing location → dative. Motion by itself isn't the test — Ich gehe im Park spazieren stays dative, because the location never changes even though there's plenty of movement.
• Verbs are a useful clue as long as you read them the same way: gehen, legen, stellen usually describe reaching a new location — accusative; sein, liegen, stehen usually describe an existing location — dative.
• Hängen is really two verbs that happen to be spelled the same: transitive hängen ("hang something up," hängte, hat gehängt) takes accusative, intransitive hängen ("be hanging," hing, hat gehangen) takes dative.
• Common contractions: am/ans (an dem/an das), im/ins (in dem/in das), and aufs (auf das) — only dem/das contract, never der or den.