Learn Hardcore German: Ich verliere manchmal meinen Schlüssel im Haus.

Because Schlüssel is a masculine noun and here it’s the direct object of the verb. German uses the accusative case for direct objects. The masculine singular accusative ending on a possessive pronoun is -en, so mein becomes meinen.

In im Haus, why is im used instead of in dem or in das?

in is a two‑way preposition that takes either dative or accusative depending on context. Here it indicates a static location (where something happens), so it takes the dative. Haus is neuter, so dative singular is dem Haus. Germans contract in dem to im. Using the accusative (in das Haus) would imply movement into the house.

Why doesn’t the sentence use a preposition with verlieren, for example verliere an?

verlieren is a fully transitive verb that directly takes an object in the accusative. You simply lose something (ich verliere etwas). There’s no extra preposition needed, unlike some verbs (e.g., warten auf).

Why is manchmal placed between the verb and the object, and could it appear elsewhere?

German frequency adverbs typically come right after the conjugated verb and before objects or other adverbials. Thus Ich verliere manchmal meinen Schlüssel is standard. You can move manchmal to the front for emphasis (Manchmal verliere ich meinen Schlüssel im Haus) or, less commonly, to the end in colloquial speech.

What’s the difference between im Haus and zu Hause? Could I say Ich verliere meinen Schlüssel zu Hause?

im Haus literally means in the house, referring specifically to the interior of a building. zu Hause means at home in a more general sense (inside or around your home). So im Haus pinpoints a location, while zu Hause refers to being at one’s home in general.

Why is the present tense used here instead of the perfect tense?

In German, the present tense often covers habitual or repeated actions. Ich verliere manchmal meinen Schlüssel describes a recurring problem (habit), so the present is natural. For a single past incident you would use the perfect: Ich habe meinen Schlüssel im Haus verloren.

Could I use verlegen instead of verlieren? What’s the difference?

verlegen means to misplace, implying you’ve put something somewhere you later can’t recall. verlieren means to lose in a more general or permanent sense. If you usually find the key again, you might hear Ich verlege meinen Schlüssel im Haus, but verlieren is more common for lost items.

Should there be a comma before im Haus?

No. German commas separate clauses, not simple phrases. im Haus is just a prepositional phrase, not an independent or subordinate clause, so you don’t put a comma before it.