Ich spreche morgen mit meiner Kollegin im Büro.

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Breakdown of Ich spreche morgen mit meiner Kollegin im Büro.

• mit: with
• morgen: tomorrow
• mein: my; (masculine or neuter, nominative)

Questions & Answers about Ich spreche morgen mit meiner Kollegin im Büro.

Why is it meiner Kollegin and not meine Kollegin?

Because mit always takes the dative case. Kollegin is feminine, and the dative feminine form of the possessive mein is meiner. So: mit meiner Kollegin = with my (female) colleague. For comparison: masculine/neuter dative would be mit meinem …, plural dative mit meinen … (and the noun usually adds -n in the dative plural if it doesn’t already end in -n).

What does im mean?

im is the contraction of in dem. You use it here because you’re talking about being located inside a place (the office), which calls for dative: in dem Büro → im Büro.

Why is it dative with in here? When would it be accusative?

German two-way prepositions (like in, auf, an) take:

• Dative for location (answering “where?”): im Büro (in the office).
• Accusative for direction/motion (answering “where to?”): ins Büro (into the office). Your sentence describes where the speaking will happen, not movement.

Can I start the sentence with Morgen?