Friendship is a relationship and concern between individuals and provides positive emotional support. Friends care for one another and look out for each other. In order for a deep understanding to occur between friends it requires opening up about personal things, listening carefully, and being loyal to one another (Kheterpal, 2008) Friendship and association are often thought of as spanning across the same continuum and are sometimes viewed as weaknesses. The study of friendship is included in the fields of sociology, social psychology, anthropology, philosophy, and zoology. Various academic theories of friendship have been proposed, among which are social exchange theory, equity theory, relational dialectics, and attachment styles.
Friendship was a topic of moral philosophy much discussed by Plato, Aristotle, and the Stoics, but less so in the modern era, until the re-emergence of contextualist and feminist approaches to ethics. In friendship, an "openness" of each to the other is found that can be seen as an enlargement of the self. Aristotle writes that "the excellent person is related to his friend in the same way as he is related to himself, since a friend is another self; and therefore, just as his own being is choiceworthy him, the friend's being is choice-worthy for him in the same or a similar way." In Ancient Greek, friend and lover are the same word.
Friendship therefore opens the door to an escape from egoism or belief that the rational course of action is always to pursue one's own self-interest, although escaping through the door would require finding what is covered by Aristotle's "same or similar way". It is notable that friendship requires sentiments to which Kant denies moral importance. It is a purely personal matter, requiring virtue, yet which runs counter to the universalistic requirement of impartial treatment of all, for a friend is someone who is treated differently from others. One problem is to reconcile these apparently
In the sequence of the emotional development of the individual, friendships come after parental bonding and before the pair bonding engaged in at the approach of maturity. In the intervening period between the end of early childhood and the onset of full adulthood, friendships are often the most important relationships in the emotional life of the adolescent and are often more intense than relationships later in life. However, making friends seems to trouble a lot of people; having no friends can be emotionally damaging in some cases.
A study by researchers from Purdue University found that post-secondary-education friendships (e.g., college, university) last longer than the friendships before it.
Children with disorders such as High-functioning autism or Asperger's syndrome usually have some difficulty forming friendships. This is due to the autistic nature of some of their symptoms, which include, but are not limited to, preferring routine actions to change, obsessive interests and rituals, and usually lacking good social skills. This does not mean that they are not able to form friendships, however. With time, moderation, and proper instruction, they are able to form friendships after realizing their own strengths and weaknesses. Children with ADHD may not have difficulty forming friendships, but they may have a hard time keeping friendships because of impulsive behaviour and hyperactivity. Children with inattentive ADD may not have as much trouble keeping and maintaining friendships, but inattentiveness may make it more difficult. Children with conditions such as Asperger's syndrome may find it easier to form a strong friendship with a child who has a condition such asADHD due to similar interests and behaviours.