Breakdown of Hij is vertrokken, want hij heeft zich bedacht.
zijn
to be
hij
he / it (referring to a 'de'-word)
hebben
to have
vertrekken
to leave / to depart
Questions & Answers about Hij is vertrokken, want hij heeft zich bedacht.
Why does the second part say heeft zich bedacht instead of is zich bedacht?
This is the golden rule for reflexive verbs! All reflexive verbs (verbs that take a reflexive pronoun like zich, me, or je) always use the helping verb hebben in the present perfect tense.
Wait, if the second part uses heeft, why does the first part say is vertrokken?
The verb vertrekken (to leave) is not reflexive. It describes a change of location, so it uses zijn (to be) as its helping verb. This sentence perfectly contrasts how motion verbs use zijn, while reflexive verbs must use hebben.
Does zich bedenken literally translate to "to think himself"?
Not quite. The non-reflexive base verb bedenken means "to invent" or "to come up with" an idea. But when you add the reflexive pronoun to make it zich bedenken, the meaning changes completely to "to change one's mind".
Why isn't the verb pushed to the end of the sentence after want (because)?
The conjunction want connects two main sentences without changing their normal word order. If you used the other Dutch word for "because", omdat, the verbs would be pushed to the end: ...omdat hij zich heeft bedacht.