Non-monogamy is a blanket term

Umbrella term

An umbrella term is a word that provides a superset or grouping of concepts that all fall under a single common category. Umbrella term is also called a hypernym. For example, cryptology is an umbrella term that encompasses cryptography and cryptanalysis, among other fields...

 which covers several types of interpersonal relationship

Interpersonal relationship

An interpersonal relationship is an association between two or more people that may range from fleeting to enduring. This association may be based on limerence, love, solidarity, regular business interactions, or some other type of social commitment. Interpersonal relationships are formed in the...

s in which an individual forms multiple and simultaneous sexual

Human sexuality

Human sexuality is the awareness of gender differences, and the capacity to have erotic experiences and responses. Human sexuality can also be described as the way someone is sexually attracted to another person whether it is to opposite sexes , to the same sex , to either sexes , or not being...

 and/or romantic

Romantic love

Romance is the pleasurable feeling of excitement and mystery associated with love.In the context of romantic love relationships, romance usually implies an expression of one's love, or one's deep emotional desires to connect with another person....

 bonds. This can be contrasted with its opposite, monogamy

Monogamy

Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...

, and yet may arise from the same psychology. The term has been criticized as it may evoke to imply that monogamy is the norm and that any other way of relating is somehow a deviation of that norm.

Types of non-monogamy

Many non-monogamous terms are flexible in definition, because they are based on criteria such as 'relationship' or 'love' that are themselves variably defined. In addition, usage creates distinctions beyond the raw definitions of the words. Thus, even though some relationships might technically be considered both polygamous and polyamorous, 'polygamy' usually signifies a codified form of multiple marriage, based on established religious teachings, while 'polyamory' is based on the preferences of the participants rather than social custom or established precedent.

Forms of non-monogamy include:

• casual relationship
  Casual relationship
  A casual relationship, colloquially known as a fling, is a physical and emotional relationship between two people who may have a sexual relationship or a near-sexual relationship without necessarily demanding or expecting the extra commitments of a more formal romantic relationship...
  
   a physical and emotional relationship between two unmarried people who may have a sexual relationship
• group marriage
  Group marriage
  Group marriage, also known as multi-lateral marriage, is a form of polyamory in which more than two persons form a family unit, with all the members of the group marriage being considered to be married to all the other members of the group marriage, and all members of the marriage share parental...
  
   (also termed polygynandry), in which several people form a single family unit, with all considered to be married to one another
• group sex
  Group sex
  Group sex is sexual behavior involving more than two participants. Group sex can occur amongst people of all sexual orientations and genders...
  
   and orgies
  Orgy
  In modern usage, an orgy is a sex party where guests engage in promiscuous or multifarious sexual activity or group sex. An orgy is similar to debauchery, which refers to excessive indulgence in sensual pleasures....
  
   involving more than two participants at the same time
• Line families, a form of group marriage intended to outlive its original members by ongoing addition of new spouses
• ménage à trois
  Ménage à trois
  Ménage à trois is a French term which originally described a domestic arrangement in which three people having sexual relations occupy the same household – the phrase literally translates as "household of three"...
  
  , a sexual (or sometimes domestic) arrangement involving three people
• open marriage
  Open marriage
  Open marriage typically refers to a marriage in which the partners agree that each may engage in extramarital sexual relationships, without this being regarded as infidelity. There are many different styles of open marriage, with the partners having varying levels of input on their spouse's...
  
   and open relationship
  Open relationship
  An open relationship is an interpersonal relationship in which the parties want to be together but agree to a form of a non-monogamous relationship. This means that they agree that a romantic or sexual relationship with another person is accepted, permitted, or tolerated...
  
  s, in which one or both members of a committed couple may become sexually active with other partners
• polyamory
  Polyamory
  Polyamory is the practice, desire, or acceptance of having more than one intimate relationship at a time with the knowledge and consent of everyone involved....
  
  , in which participants have multiple romantic partners
• poly families, similar to group marriage, but some members may not consider themselves married to all other members
• polyfidelity
  Polyfidelity
  Polyfidelity is a form of polyamory where all members are considered equal partners and agree to be sexually active only with other members of the group. The term originated in the Kerista Village commune in San Francisco which practiced polyfidelity from 1971 to 1991...
  
  , in which participants have multiple partners but restrict sexual activity to within a certain group
• polygamy
  Polygamy
  Polygamy is a marriage which includes more than two partners...
  
  , in which one person in a relationship has married multiple partners
• polyandry
  Polyandry
  Polyandry refers to a form of marriage in which a woman has two or more husbands at the same time. The form of polyandry in which a woman is married to two or more brothers is known as "fraternal polyandry", and it is believed by many anthropologists to be the most frequently encountered...
  
  , in which women have multiple husbands
• polygyny
  Polygyny
  Polygyny is a form of marriage in which a man has two or more wives at the same time. In countries where the practice is illegal, the man is referred to as a bigamist or a polygamist...
  
  , in which men have multiple wives
• plural marriage
  Plural marriage
  Polygamy was taught by leaders of The Church of Jesus Christ of Latter-day Saints for more than half of the 19th century, and practiced publicly from 1852 to 1890.The Church's practice of polygamy has been highly controversial, both within...
  
  , a form of polygyny associated with the Latter Day Saint movement
  Latter Day Saint movement
  The Latter Day Saint movement is a group of independent churches tracing their origin to a Christian primitivist movement founded by Joseph Smith, Jr. in the late 1820s. Collectively, these churches have over 14 million members...
  
   in the 19th-century and with present-day splinter groups from that faith. It is also associated with an evangelical splinter group which advocates Christian Plural Marriage
  Christian Plural Marriage
  Polygamy in Christianity is a not a form of marriage that is generally accepted within Christianity. There are numerous examples of polygamy in Old Testament...
  
  
• relationship anarchy, which do not divide relationships of partners and non-partners, but have a more flexible approach to relationships where everything is allowed so long as everyone can accept the agreement.
• swinging
  Swinging
  Swinging or partner swapping is a non-monogamous behavior, in which both partners in a committed relationship agree, as a couple, for both partners to engage in sexual activities with other couples as a recreational or social activity...
  
  , similar to open relationships, but commonly conducted as an organised social activity