Love is any of a number of emotions and experiences related to a sense of strong affection and attachment. The word love can refer to a variety of different feelings, states, and attitudes, ranging from generic pleasure ("I loved that meal") to intense interpersonal attraction ("I love my boyfriend"). This diversity of uses and meanings, combined with the complexity of the feelings involved, makes love unusually difficult to consistently define, even compared to other emotional states.
Love is an extremely powerful emotion; it can be irresistible and people are often bound to pursue their love interests. Love is a major theme in literature, poetry, and film.
As an abstract concept, love usually refers to a deep, ineffable feeling of tenderly caring for another person. Even this limited conception of love, however, encompasses a wealth of different feelings, from the passionate desire and intimacy of romantic love to the nonsexual emotional closeness of familial and platonic love to the profound oneness or devotion of religious love. 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.
The English word "love" can have a variety of related but distinct meanings in different contexts. Often, other languages use multiple words to express some of the different concepts that English relies mainly on "love" to encapsulate; one example is the plurality of Greek words for "love." Cultural differences in conceptualizing love thus make it doubly difficult to establish any 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. As a general expression of positive sentiment (a stronger form of like), love 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; and as an interpersonal relationship with romantic overtones, love is commonly contrasted with friendship, although other definitions of the word love may be applied to close friendships in certain contexts.
When discussed in the abstract, love usually refers to interpersonal love, an experience felt by a person for another person. Love often involves caring for or identifying with a person or thing, 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.
Because of the complex and abstract nature of love, discourse on love is commonly reduced to a thought-terminating cliché, and there are a number of common proverbs regarding love, from Virgil's "Love conquers all" to the Beatles' "All you need is love." Bertrand Russell describes love as a condition of "absolute value," as opposed to relative value. Theologian Thomas Jay Oord said that to love is to "act intentionally, in sympathetic response to others, to promote overall well-being." Philosopher Gottfried Leibniz said that love is "to be delighted by the happiness of another."
A person can be said to love a country, principle, or goal if they value it greatly and are deeply committed to it. Similarly, compassionate outreach and volunteer workers' "love" of their cause may sometimes be borne not of interpersonal love, but impersonal love coupled with altruism and strong political convictions. 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, this condition is called paraphilia.
Interpersonal love refers to love between human beings. It is a more potent sentiment than a simple liking for another. Unrequited love refers to those feelings of love that are not reciprocated. Interpersonal love is most closely associated with interpersonal relationships. 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 last century, the science of psychology has written a great deal on the subject. In recent years, the sciences of evolutionary psychology, evolutionary biology, anthropology, neuroscience, and biology have added to the understanding of the nature and function of love.
Biological models of sex tend to view love as a mammalian drive, much like hunger or thirst. Helen Fisher, a leading expert in the topic of love, divides the experience of love into three partly overlapping stages: lust, attraction, and attachment. Lust exposes people to others; romantic attraction encourages people to focus their energy on mating; and attachment involves tolerating the spouse (or indeed the child) long enough to rear a child into infancy.
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 pheromones, dopamine, norepinephrine, and serotonin, which act in a manner similar to amphetamines, 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 on 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.
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 and most common 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. American psychologist Zick Rubin seeks to define love by psychometrics. His work states that three factors constitute love: attachment, caring, and intimacy. 
Following developments in electrical theories such as Coulomb's law, which showed that positive and negative charges attract, analogs in human life were developed, such as "opposites attract." Over the last century, research on the nature of human mating has generally found this not to be true when it comes to character and personality—people tend to like people similar to themselves. However, in a few unusual and specific domains, such as immune systems, it seems that humans prefer others who are unlike themselves (e.g., with an orthogonal immune system), since this will lead to a baby that has the best of both worlds. In recent years, various human bonding theories have been developed, described in terms of attachments, ties, bonds, and affinities.
Some Western authorities disaggregate into two main components, the altruistic and the narcissistic. This view is represented in the works of Scott Peck, whose work in the field of applied psychology explored the definitions of love and evil. Peck maintains that love is a combination of the "concern for the spiritual growth of another," and simple narcissism. In combination, love is an activity, not simply a feeling.
Comparison of scientific models
Biological models of love tend to see it as a mammalian drive, similar to hunger or thirst. Psychology sees love as more of a social and cultural phenomenon. There are probably elements of truth in both views. Certainly love is influenced by hormones (such as oxytocin), neurotrophins (such as NGF), and pheromones, and how people think and behave in love is influenced by their conceptions of love. The conventional view in biology is that there are two major drives in love: sexual attraction and attachment. Attachment between adults is presumed to work on the same principles that lead an infant to become attached to its mother. The traditional psychological view sees love as being a combination of companionate love and passionate love. Passionate love is intense longing, and is often accompanied by physiological arousal (shortness of breath, rapid heart rate); companionate love is affection and a feeling of intimacy not accompanied by physiological arousal.
Studies have shown that brain scans of those infatuated by love display a resemblance to those with a mental illness. Love creates activity in the same area of the brain where hunger, thirst, and drug cravings create activity. New love, therefore, could possibly be more physical than emotional. Over time, this reaction to love mellows, and different areas of the brain are activated, primarily ones involving long-term commitments. Dr. Andrew Newberg, a neuroscientist, suggests that this reaction to love is so similar to that of drugs because without love, humanity would die out.
- Even after all this time
- The sun never says to the earth, "You owe me."
- Look what happens with a Love like that!
- —It lights the whole Sky. (Hafiz)
Rumi, Hafez and Sa'di are icons of the passion and love that the Persian culture and language present. The Persian word for love is eshgh, deriving from the Arabic ishq. In the Persian culture, everything is encompassed by love and all is for love, starting from loving friends and family, husbands and wives, and eventually reaching the divine love that is the ultimate goal in life.
Chinese and other Sinic cultures
In contemporary Chinese language and culture, several terms or root words are used for the concept of love:
- It was the first name of the Qing emperor.
- Ai (愛) is used as a verb (e.g., Wo ai ni, "I love you") or as a noun, especially in aiqing (愛情), "love" or "romance." In mainland China since 1949, airen (愛人, originally "lover," or more literally, "love person") is the dominant word for "spouse" (with separate terms for "wife" and "husband" originally being de-emphasized); the word once had a negative connotation, which it retains among many in Taiwan.
- Lian (戀) is not generally used alone, but instead as part of such terms as "being in love" (談戀愛, tan lian'ai—also containing ai), "lover" (戀人, lianren) or "homosexuality" (同性戀, tongxinglian).
- Qing (情), commonly meaning "feeling" or "emotion," often indicates "love" in several terms. It is contained in the word aiqing (愛情); qingren (情人) is a term for "lover."
In Confucianism, lian is a virtuous benevolent love. Lian should be pursued by all human beings, and reflects a moral life. The Chinese philosopher Mozi developed the concept of ai (愛) in reaction to Confucian lian. Ai, in Mohism, is universal love towards all beings, not just towards friends or family, without regard to reciprocation. Extravagance and offensive war are inimical to ai. Although Mozi's thought was influential, the Confucian lian is how most Chinese conceive of love.
Gănqíng (感情) is the "feeling" of a relationship, vaguely similar to empathy. A person will express love by building good gănqíng, accomplished through helping or working for another and emotional attachment toward another person or anything.
Yuanfen (緣份) is a connection of bound destinies. A meaningful relationship is often conceived of as dependent on strong yuanfen. It is very similar to serendipity. A similar conceptualization in English is, "They were made for each other," "fate," or "destiny."
Zaolian (Simplified: 早恋, Traditional: 早戀, pinyin: zǎoliàn), literally "early love," is a contemporary term in frequent use for romantic feelings or attachments among children or adolescents. Zaolian describes both relationships among a teenage boyfriend and girlfriend as well as the "crushes" of early adolescence or childhood. The concept essentially indicates a prevalent belief in contemporary Chinese culture, which is that, due to the demands of their studies (especially true in the highly competitive educational system of China), youth should not form romantic attachments lest they jeopardize their chances for future success. Reports have appeared in Chinese newspapers and other media detailing the prevalence of the phenomenon and its perceived dangers to students and the fears of parents.
Greek distinguishes several different senses in which the word "love" is used. For example, Ancient Greek has the words philia, eros, agape, storge, and xenia. However, with Greek (as with many other languages), it has been historically difficult to separate the meanings of these words totally. At the same time, the Ancient Greek text of the Bible has examples of the verb agapo having the same meaning as phileo.
Agape (ἀγάπη agápē) means love in modern-day Greek. The term s'agapo means I love you in Greek. The word agapo is the verb I love. It generally refers to a "pure," ideal type of love, rather than the physical attraction suggested by eros. However, there are some examples of agape used to mean the same as eros. It has also been translated as "love of the soul."
Eros (ἔρως érōs) is passionate love, with sensual desire and longing. The Greek word erota means in love. Plato refined his own definition. Although eros is initially felt for a person, with contemplation it becomes an appreciation of the beauty within that person, or even becomes appreciation of beauty itself. Eros helps the soul recall knowledge of beauty and contributes to an understanding of spiritual truth. Lovers and philosophers are all inspired to seek truth by eros. Some translations list it as "love of the body."
Philia (φιλία philía), a dispassionate virtuous love, was a concept developed by Aristotle. It includes loyalty to friends, family, and community, and requires virtue, equality, and familiarity. Philia is motivated by practical reasons; one or both of the parties benefit from the relationship. It can also mean "love of the mind."
Storge (στοργή storgē) is natural affection, like that felt by parents for offspring.
Xenia (ξενία xenía), hospitality, was an extremely important practice in Ancient Greece. It was an almost ritualized friendship formed between a host and his guest, who could previously have been strangers. The host fed and provided quarters for the guest, who was expected to repay only with gratitude. The importance of this can be seen throughout Greek mythology—in particular, Homer's Iliad and Odyssey.
Turkish (Shaman & Islamic)
In Turkish, the word "love" comes up with several meanings. A person can love a god, a person, parents, or family. But that person can "love" just one person from the opposite sex, which they call the word "aşk." Aşk is a feeling for to love, as it still is in Turkish today. The Turks used this word just for their loves in a romantic or sexual sense. If a Turk says that he is in love (aşk) with somebody, it is not a love that a person can feel for his or her parents; it is just for one person, and it indicates a huge infatuation. The word is also common for Turkic languages, such as Azerbaijani (eşq) and Kazakh (ғашық).
Ancient Roman (Latin)
The Latin language has several different verbs corresponding to the English word "love."
Amāre is the basic word for to love, as it still is in Italian today. The Romans used it both in an affectionate sense as well as in a romantic or sexual sense. From this verb come amans—a lover, amator, "professional lover," often with the accessory notion of lechery—and amica, "girlfriend" in the English sense, often as well being applied euphemistically to a prostitute. The corresponding noun is amor, which is also used in the plural form to indicate love affairs or sexual adventures. This same root also produces amicus—"friend"—and amicitia, "friendship" (often based to mutual advantage, and corresponding sometimes more closely to "indebtedness" or "influence"). Cicero wrote a treatise called On Friendship (de Amicitia), which discusses the notion at some length. Ovid wrote a guide to dating called Ars Amatoria (The Art of Love), which addresses, in depth, everything from extramarital affairs to overprotective parents.
Complicating the picture somewhat, Latin sometimes uses amāre where English would simply say to like. This notion, however, is much more generally expressed in Latin by placere or delectāre, which are used more colloquially, the latter used frequently in the love poetry of Catullus.
Diligere often has the notion "to be affectionate for," "to esteem," and rarely if ever is used for romantic love. This word would be appropriate to describe the friendship of two men. The corresponding noun diligentia, however, has the meaning of "diligence" or "carefulness," and has little semantic overlap with the verb.
Observare is a synonym for diligere; despite the cognate with English, this verb and its corresponding noun, observantia, often denote "esteem" or "affection."
Caritas is used in Latin translations of the Christian Bible to mean "charitable love"; this meaning, however, is not found in Classical pagan Roman literature. As it arises from a conflation with a Greek word, there is no corresponding verb.
In Hebrew, Ahava is the most commonly used term for both interpersonal love and love of God.
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- Love letter
- Haptic medicine
- A General Theory of Love, provides a social, historical, and biomedical framework overview of love.
- The Science of Love
- A whimsical overview of scientific research on love, with references