Friend - Partner - Lover - Soulmate

friend (frĕnd) 1. a person known well to another and regarded with liking, affection, and loyalty.
part·ner (pärt'nər) 1. one that is united or associated with another, an ally or companion
lov·er (lŭv'ər) 1. one who loves another, especially one who feels sexual love. 2. lovers a couple in love with each other.

soulmate (or soul mate) 1. a term sometimes used to designate someone with whom one has a feeling of deep and natural affinity, friendship, love, intimacy, sexiuality and/or compatibility.