Love encompasses a variety of strong and positive emotional and mental states, ranging from the most sublime virtue or good habit, the deepest interpersonal affection and to the simplest pleasure. An example of this range of meanings is that the love of a mother differs from the love of a spouse differs from the love of food. Most commonly, love refers to a feeling of strong attraction and emotional attachment. Love can also be a virtue representing human kindness, compassion, and affection, as "the unselfish loyal and benevolent concern for the good of another". It may also describe compassionate and affectionate actions towards other humans, one's self or animals.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 has been postulated to be a function to keep human beings together against menaces and to facilitate the continuation of the species.Ancient Greek philosophers identified five forms of love: essentially, familial love (in Greek, Storge), friendly love (Philia), romantic love (Eros), guest love (Xenia) and divine love (Agape). Modern authors have distinguished further varieties of love: unrequited love, infatuated love, self-love, and courtly love. Asian cultures have also distinguished Ren, Kama, Bhakti, Mettā, Ishq, Chesed, and other 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.