Scientific research on emotion has increased significantly over the past two decades

The color wheel theory of love defines three primary, three secondary and nine tertiary love styles, describing them in terms of the traditional color wheel. The triangular theory of love suggests "intimacy, passion and commitment" are core components of love. 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. The word "love" can have a variety of related but distinct meanings in different contexts. Many other languages use multiple words to express some of the different concepts that in English are denoted as "love"; one example is the plurality of Greek words for "love" which includes agape and eros.[12] Cultural differences in conceptualizing love thus doubly impede the establishment of a universal definition. Although the nature or essence of love is a subject of frequent debate, different aspects of the word can be clarified by determining what isn't love (antonyms of "love"). Love as a general expression of positive sentiment (a stronger form of like) is commonly contrasted with hate (or neutral apathy). As a less-sexual and more-emotionally intimate form of romantic attachment, love is commonly contrasted with lust. As an interpersonal relationship with romantic overtones, love is sometimes contrasted with friendship, although the word love is often applied to close friendships or platonic love. (Further possible ambiguities come with usages "girlfriend", "boyfriend", "just good friends"). ----

---- Fraternal love (Prehispanic sculpture from 250–900 AD, of Huastec origin). Museum of Anthropology in Xalapa, Veracruz, Mexico Abstractly discussed, love usually refers to an experience one person feels for another. Love often involves caring for, or identifying with, a person or thing (cf. vulnerability and care theory of love), including oneself (cf. narcissism). In addition to cross-cultural differences in understanding love, ideas about love have also changed greatly over time. Some historians date modern conceptions of romantic love to courtly Europe during or after the Middle Ages, although the prior existence of romantic attachments is attested by ancient love poetry. The complex and abstract nature of love often reduces discourse of love to a thought-terminating cliché. Several common proverbs regard love, from Virgil's "Love conquers all" to The Beatles' "All You Need Is Love". St. Thomas Aquinas, following Aristotle, defines love as "to will the good of another." Bertrand Russell describes love as a condition of "absolute value," as opposed to relative value.[citation needed] Philosopher Gottfried Leibniz said that love is "to be delighted by the happiness of another.Meher Baba stated that in love there is a "feeling of unity" and an "active appreciation of the intrinsic worth of the object of love."Biologist Jeremy Griffith defines love as "unconditional selflessness". Impersonal People can be said to love an object, principle, or goal to which they are deeply committed and greatly value. For example, compassionate outreach and volunteer workers' "love" of their cause may sometimes be born not of interpersonal love but impersonal love, altruism, and strong spiritual or political convictions.[19] People can also "love" material objects, animals, or activities if they invest themselves in bonding or otherwise identifying with those things. If sexual passion is also involved, then this feeling is called paraphilia.[20] A common principle that people say they love is life itself. Interpersonal love refers to love between human beings. It is a much more potent sentiment than a simple liking for a person. Unrequited love refers to those feelings of love that are not reciprocated. Interpersonal love is most closely associated with Interpersonal relationships.[19] Such love might exist between family members, friends, and couples. There are also a number of psychological disorders related to love, such as erotomania. Throughout history, philosophy and religion have done the most speculation on the phenomenon of love. In the 20th century, the science of psychology has written a great deal on the subject. In recent years, the sciences of psychology, anthropology, neuroscience Biological models of sex tend to view love as a mammalian drive, much like hunger or thirst.[21] Helen Fisher, an anthropologist and human behavior researcher, divides the experience of love into three partly overlapping stages: lust, attraction, and attachment. Lust is the feeling of sexual desire; romantic attraction determines what partners mates find attractive and pursue, conserving time and energy by choosing; and attachment involves sharing a home, parental duties, mutual defense, and in humans involves feelings of safety and security. Three distinct neural circuitries, including neurotransmitters, and three behavioral patterns, are associated with these three romantic styles. Lust is the initial passionate sexual desire that promotes mating, and involves the increased release of chemicals such as testosterone and estrogen. These effects rarely last more than a few weeks or months. Attraction is the more individualized and romantic desire for a specific candidate for mating, which develops out of lust as commitment to an individual mate forms. Recent studies in neuroscience have indicated that as people fall in love, the brain consistently releases a certain set of chemicals, including the neurotransmitter hormones, dopamine, norepinephrine, and serotonin, the same compounds released by amphetamine, stimulating the brain's pleasure center and leading to side effects such as increased heart rate, loss of appetite and sleep, and an intense feeling of excitement. Research has indicated that this stage generally lasts from one and a half to three years. ----

---- Since the lust and attraction stages are both considered temporary, a third stage is needed to account for long-term relationships. Attachment is the bonding that promotes relationships lasting for many years and even decades. Attachment is generally based on commitments such as marriage and children, or mutual friendship based on things like shared interests. It has been linked to higher levels of the chemicals oxytocin and vasopressin to a greater degree than short-term relationships have. Enzo Emanuele and coworkers reported the protein molecule known as the nerve growth factor (NGF) has high levels when people first fall in love, but these return to previous levels after one year. ----

---- Psychology depicts love as a cognitive and social phenomenon. Psychologist Robert Sternberg formulated a triangular theory of love and argued that love has three different components: intimacy, commitment, and passion. Intimacy is a form in which two people share confidences and various details of their personal lives, and is usually shown in friendships and romantic love affairs. Commitment, on the other hand, is the expectation that the relationship is permanent. The last form of love is sexual attraction and passion. Passionate love is shown in infatuation as well as romantic love. All forms of love are viewed as varying combinations of these three components. Non-love does not include any of these components. Liking only includes intimacy. Infatuated love only includes passion. Empty love only includes commitment. Romantic love includes both intimacy and passion. Companionate love includes intimacy and commitment. Fatuous love includes passion and commitment. Lastly, consummate love includes all three components. American psychologist Zick Rubin sought to define love by psychometrics in the 1970s. His work states that three factors constitute love: attachment, caring, and intimacy.