festejar
celebrate
festive
joyous or merry, often related to a celebration
+
-ar
verb suffix
Festejar means to celebrate and can be thought of as making something festive0 (joyous or merry0) + -ar1 (verb1).
verb
  1. celebrate
    To celebrate or commemorate an event or occasion
    Vamos a festejar tu cumpleaños este fin de semana. // We're going to celebrate your birthday this weekend.