Dictionary.com:
Soulmate (or soul mate) is a term sometimes used to designate someone with whom one has a feeling of deep and natural affinity, friendship, love, intimacy, sexuality, and/or compatibility. A related concept is that of the twin flame or twin soul – thought to be the ultimate soulmate, the one and only other half of one's soul, for which all souls are driven to find and join. However, not everyone who uses these terms intends them to carry such mystical connotations.
Soul lovers – someone you love, and would do anything for, and someone who loves you, and would do anything for you. And in that love, nothing is required for either person, because everything is already given. You love them more than anything in the world and could not live without them.
Soul sister/brother – someone belonging in the same soul group as you and therefore having an unusually strong bond and likeness to you
Classical – Greek mythology – Originally humans were combined of four arms, four legs, and a single head made of two faces, but Zeus feared their power and split them all in half, condemning them to spending their lives searching for the other half to complete them. This theory was presented as a half-serious story by Aristophanes in Plato's Symposium, after all the participants at the Symposium ("drinking party") were charged to philosophize on the topic of love.
Spiritual and religious – concepts of reincarnation and karma. Soulmates have spent many previous lifetimes together.
Karmic soulmate – someone who has a special mission or influence on one's life
Companion soulmate – People with whom one has made a connection.
Twin soulmates – Very close friends with whom one has strong bonds.
Twin flame soulmate – A popular romantic belief that there is only one true soulmate.
