This is an irregular verb. It is a highly irregular verb.
PresentPresente
Voy al mercado los sábados por la mañana.
I go to the market on Saturday mornings.
PreteritePretérito indefinido
Fuimos a verla ayer.
We went to see her yesterday.
ImperativeImperativo afirmativo
Vayan sin mí.
Go ahead without me.
Present SubjunctivePresente de subjuntivo
Quiero que vayas a París conmigo.
I want you to go to Paris with me.