Vide, kende or kunne

English to know has three Danish partners, and they cannot replace each other.

• vide (present ved): know a fact. It is followed by a clause with at, hvad, hvor, hvem, om or by det: Jeg ved ikke, hvor hun bor (I don't know where she lives).
• kende (present kender): know a person, a place or a thing, be familiar with it: Kender du min søster? (Do you know my sister?)
• kunne (present kan): know something you have learned, above all a language: Kan du tysk? (Do you know German?)

Quick test: if a question word or at follows the verb, use ved. If a person or a place follows, use kender. If a language follows, use kan.