Friendship is a share of mutual affection between two or more people. It is a stronger version of interpersonal bond as compared to a simple acquaintance. Friendship has been scrutinized in academic fields including social psychology, philosophy, sociology and anthropology. Several academic theories about friendship have been proposed, for example the social exchange theory, equity theory, attachment styles and relational dialectics.
Although there are many forms of friendship, varying from place to place, certain traits are present in most kinds of friendship. These characteristics include sympathy, empathy, honesty, affection, altruism, mutual understanding and compassion and enjoyment of one another's company, the ability to be one self, and make mistakes without fear of judgment from the friend and trust
Agentic friendship - In an agentic friendship, both the persons involved expect each other to help achieve practical goals in their personal as well as professional lives. Agentic friends may help with studying for an exam, completing projects, or helping move houses. They cherish sharing time together, but that is only when they have time available to help each other. These relationships usually do not include the sharing of emotions or personal information.
Best friend - Best friends share extremely strong interpersonal ties with each other. They share almost everything with each other and are most comfortable in each other’s presence. The bond between two best friends is perhaps the strongest of all the different bonds.
Blood brother or sister - This term can either denote people related by birth or to friends who swear their loyalty by mixing their blood together. The latter has been practiced and through history. However, it is rarely continued today due to the different dangers of blood-borne diseases.
Buddy - Generally used as a synonym for friend, "buddy" can refer to a specific friend or partner with whom one can engage in a particular activity, such as a "study buddy."
Communal friendship - Defined by Steven McCornack, this is a relationship in which friends often gather to provide emotional support and encouragement in times of great need. This type of friendship lasts only when the parties involved fulfill the expectations of the ones in need of support.
Comrade - This term denotes a friend, colleague, or an ally, specifically in a military or political context. Comradeship may arise in the time of war, or when people have common goal or a mutual enemy. These leads to friendships in circumstances where ordinary friendships may not have formed. In English, this term is associated with the Soviet Union.
Family friend - This term denotes the friend of a family member or the family member of a friend.
Frenemy - A fusion of the words "friend" and "enemy," the term "frenemy" refers to either an enemy who is disguised as a friend (wolf in sheep's clothing) or a person who is both a rival and a friend. This may take the form of a strange bond and a love–hate relationship.
Imaginary friend - An imaginary friend is a friend who is not physically present. It is usually associated with a child. These friends may either be human or animal, such as the human-sized rabbit as seen in the 1950 film Harvey. Creation of an imaginary friend may be seen as bad behavior or even taboo. However it is most commonly regarded as harmless and typical childhood behavior.
Internet relationship - An internet friendship is a form of friendship or sometimes romance which takes place exclusively over the internet. This can mature into a proper and lasting friendship. Internet friendships are in similar context to pen pals, but it strengthens through chatting online while the latter through letters. People in these friendships may or may not use their true identities.
Opposite-sex friendship - Opposite-sex friendships may not always be socially accepted. Although complications arise in such relationships, opposite sex friendships can be really strong and emotionally rewarding if maintained without incident.
Pen pal - Pen pals are primarily people who communicate and maintain their relationship through mail correspondence. They may not have necessarily met each other in person. This type of friendship is encouraged in many elementary school children. It is fathomed than an outside source of information or perhaps a different person's experience would help a child become wiser. In modern times, internet relationships have largely reduced pen pals, though the practice still ensues.