This is the 110th most frequent German word.
denn
The German word "denn" means "because," "since," or is used as a particle to add emphasis or curiosity in questions (e.g., "then" or "so").
In this sentence, 'denn' is used as a particle to add emphasis or express surprise in a question, giving it a more conversational tone.
Was machst du denn hier?
What are you doing here?
Here, 'denn' is again used as a causal conjunction, indicating the reason for the action described in the first clause.
Er hat es nicht getan, denn er hatte keine Zeit.
He didn't do it, because he had no time.
In this sentence, 'denn' is used as a coordinating conjunction that expresses a causal relationship between the two clauses, explaining the reason for the statement.