If Abraham was Sari's Lord,Why do we call God & Jesus Lord?

Sarah, who is about 90 years old and has gone through menopause, laughs at God when he tells her that she will have a son. She asks God if she will "have pleasure" with her "Lord" [Abraham], when both are so very old. God ures her that he will return and impregnate her at the appointed time. 18:11-14