California Code, Elections Code - ELEC § 349

(a) “Residence” for voting purposes means a person's domicile.

(b) The domicile of a person is that place in which his or her habitation is fixed, wherein the person has the intention of remaining, and to which, whenever he or she is absent, the person has the intention of returning. At a given time, a person may have only one domicile.

(c) The residence of a person is that place in which the person's habitation is fixed for some period of time, but wherein he or she does not have the intention of remaining. At a given time, a person may have more than one residence.