Interpersonal relationship

Interpersonal relationships are social associations, connections, or affiliations between two or more people. There are different levels of intimacy and sharing concerning centered around something(s) shared in common. The study of relationships is of concern to sociology, psychology and anthropology.
Types of interpersonal relationships
Kinship relationships, including family relationships, being related to someone else by blood (consanguinity). For example, there is fatherhood or motherhood. Kinship relationships can also be made through marriage. For example, there are father-in-laws, mother-in-laws, uncles by marriage, or aunts by marriage.
Formalized intimate relationships or long-term relationships through law and public ceremony, e.g. marriage and civil union.
Non-formalized intimate relationships or long-term relationships such as loving relationships or romantic relationships with or without living together; the other person is often called lover, boyfriend or girlfriend (not to be confused with just a male or female friend). If the partners live together, the relationship may be similar to marriage, and the other person may be called husband or wife. Long term cohabiting relationships are often called common-law marriages, but in the vast majority of the world there is no such legal status. Mistress is the term for a female lover of a man who is married to another woman. She may even be an official mistress (in French maitresse en titre); an example is Madame de Pompadour.
Soulmates, individuals who are intimately drawn to one another through a favorable meeting of the minds and who find mutual acceptance and understanding with one another. Soulmates may feel themselves bonded together for a lifetime; and may be sexual partners but not necessarily.
Casual relationships, relationships extending beyond one-night stands that exclusively consist of sexual behavior, the participants of which may be known as friends with benefits or sex buddies when limited to considering sexual intercourse or sexual partners in a wider sense.
Platonic love is an affectionate relationship into which the sexual element does not enter, especially in cases where one might easily think something else.
Friendship, which consists of mutual love, trust, respect, and unconditional acceptance, and usually means that there is common ground between the individuals involved; see also internet friendship and pen pal.
Brotherhood and sisterhood, individuals united in a common cause or having a common interest, which may involve formal membership in a club, organization, association, society, lodge, fraternities and sororities. This type of interpersonal relationship also includes the comradeship of fellow soldiers in peace or war.
Partners or coworkers in a profession, business, or a common workplace.
Participation in a community, for example, a community of interest or practice.
Association, simply being introduced to someone or knowing who they are by interaction.
Factors
The discovery or establishment of common ground between individuals is a fundamental component for long lasting interpersonal relationships. Loss of common ground, which may happen over time, may tend to end interpersonal relationships.
For each relationship type, essential skills are needed, and without these skills more advanced relationships are not possible. (For example, partnership needs the skills of friendship and teamwork skills).