Friendship is a relationship of mutual affection between people. It is a stronger form of interpersonal bond than an "acquaintance" or an "association", such as a classmate, neighbor, coworker, or colleague.
A group of Germans at Allas Sea Pool, Helsinki, Finland. Traveling abroad together is a strong indicator of friendship.
In some cultures, the concept of friendship is restricted to a small number of very deep relationships; in others, such as the U.S. and Canada, a person could have many friends, and perhaps a more intense relationship with one or two people, who may be called good friends or best friends. Other colloquial terms include besties or Best Friends Forever (BFFs). Although there are many forms of friendship, some of which may vary from place to place, certain characteristics are present in many such bonds. Such features include choosing to be with one another, enjoying time spent together, and being able to engage in a positive and supportive role to one another.
Sometimes friends are distinguished from family, as in the saying "friends and family", and sometimes from lovers (e.g., "lovers and friends"), although the line is blurred with friends with benefits. Similarly, the friend zone is a term for when someone is restricted from rising up to the status of lover, hence the name (see also Unrequited love).
Friendship has been studied in academic fields, such as communication, sociology, social psychology, anthropology, and philosophy. Various academic theories of friendship have been proposed, including social exchange theory, equity theory, relational dialectics, and attachment styles.
Young childhood friends
The understanding of friendship in children tends to be more heavily focused on areas such as common activities, physical proximity, and shared expectations.: 498 [a] These friendships provide opportunity for playing and practicing self-regulation.: 246 Most children tend to describe friendship in terms of things like sharing, and children are more likely to share with someone they consider to be a friend.: 246  As children mature, they become less individualized and are more aware of others. They gain the ability to empathize with their friends, and enjoy playing in groups. They also experience peer rejection as they move through the middle childhood years. Establishing good friendships at a young age helps a child to be better acclimated in society later on in their life.
Based upon the reports of teachers and mothers, 75% of preschool children had at least one friend. This figure rose to 78% through the fifth grade, as measured by co-nomination as friends, and 55% had a mutual best friend.: 247 About 15% of children were found to be chronically friendless, reporting periods without mutual friends at least six months.: 250
Studies have shown that friendships in childhood can assist in the development of certain skills, such as building empathy and learning different problem solving techniques. Coaching from parents can be useful in helping children to make friends. Eileen Kennedy-Moore describes three key ingredients of children's friendship formation: (1) openness, (2) similarity, and (3) shared fun. Parents can also help children understand social guidelines they haven't learned on their own. Drawing from research by Robert Selman and others, Kennedy-Moore outlines developmental stages in children's friendship, reflecting an increasing capacity to understand others' perspectives: "I Want It My Way", "What's In It For Me?", "By the Rules", "Caring and Sharing", and "Friends Through Thick and Thin."
Two friends sitting together in Bhutan
In adolescence, friendships become "more giving, sharing, frank, supportive, and spontaneous." Adolescents tend to seek out peers who can provide such qualities in a reciprocal relationship, and to avoid peers whose problematic behavior suggest they may not be able to satisfy these needs. Personal characteristics and dispositions are also features sought by adolescents, when choosing whom to begin a friendship with. During adolescence, friendship relationships are more based on similar morals and values, loyalty, and shared interests than that of children, in which friendships stem from being in the same vicinity and access to playthings.: 246
One large study of American adolescents determined how their engagement in problematic behavior (such as stealing, fighting, and truancy) was related to their friendships. Findings indicated that adolescents were less likely to engage in problem behavior when their friends did well in school, participated in school activities, avoided drinking, and had good mental health. The opposite was found regarding adolescents who did engage in problematic behavior. Whether adolescents were influenced by their friends to engage in problem behavior depended on how much they were exposed to those friends, and whether they and their friendship groups "fit in" at school.
Friendships formed during post-secondary education last longer than friendships formed earlier. In late adolescence, cross-racial friendships tend to be uncommon, likely due to prejudice and cultural differences.
Friendship in adulthood
Freundschaft zwischen Jonathan und David by Julius Schnorr von Karolsfeld (1860), which translates in English as Friendship between Jonathan and David
Two friends before posing for a picture
Friendship in adulthood provides companionship, affection, as well as emotional support, and contributes positively to mental well-being and improved physical health.: 426
Adults may find it particularly difficult to maintain meaningful friendships in the workplace. "The workplace can crackle with competition, so people learn to hide vulnerabilities and quirks from colleagues. Work friendships often take on a transactional feel; it is difficult to say where networking ends and real friendship begins." Unlike younger people, many adults value their financial well-being and security that their job provides rather than developing friendships with coworkers.
The majority of adults have an average of two close friends. Numerous studies with adults suggest that friendships and other supportive relationships do enhance self-esteem.
Older adults continue to report high levels of personal satisfaction in their friendships as they age, even as the overall number of friends tends to decline. This satisfaction is associated with an increased ability to accomplish activities of daily living, as well as a reduced decline in cognitive abilities, decreased instances of hospitalization, and better outcomes related to rehabilitation.: 427 The overall number of reported friends in later life may be mediated by increased lucidity, better speech and vision, and marital status.: 53 A decline in the number of friends an individual has as they become older has been explained by Carstensen's Socioemotional Selectivity Theory, which describes a change in motivation that adults experience when socializing. The theory states that an increase in age is characterized by a shift from information-gathering to emotional regulation; in order to maintain positive emotions, older adults restrict their social groups to those whom they share an emotional bond.[