Triangular Theory of Love
A theory of love which deals both with the nature of love with loves in different kinds of relationships. It is suggested that there are 3 components: (a) intimacy encompassing the feelings of closeness, connectedness, and bondedness experienced in loving relationships; (b) passion encompassing the drives that lead to romance, physical attraction, and sexual consummation; and (c) decision/commitment encompassing, in the short term, the decision that one loves another, and in the long term, the commitment to maintain that love.
Sternberg, R. J. (1986). A triangular theory of love. Psychological Review, 93(2), 119-135. doi: 10.1037/0033-295X.93.2.119