adónde
/aˈdonde/ · A2 · adv
to where, whither, whereto
adónde = a (to) + dónde (where): to where
Spanish glues the preposition a (to) onto dónde (where), giving the direction-asking word. Use it with verbs of motion: ¿Adónde vas? = Where are you going (to)? Plain dónde asks location; adónde asks destination.