Ancient Greek philosophers identified four forms of love: essentially, familial love (in Greek, storge), friendly love (philia), romantic love (eros), and divine love (agape). Modern authors have distinguished further varieties of love: infatuated love, self-love, and courtly love. Non-Western traditions have also distinguished variants or symbioses of these states. Love has additional religious or spiritual meaning. This diversity of uses and meanings combined with the complexity of the feelings involved makes love unusually difficult to consistently define, compared to other emotional states.
Love in its various forms acts as a major facilitator of interpersonal relationships and, owing to its central psychological importance, is one of the most common themes in the creative arts.
Love may be understood as a function to keep human beings together against menaces and to facilitate the continuation of the species.