The practice of having sex with multiple partners at the same time.

A form of polygynous, polyandrous marriage in which more than one man and more than one woman form a family unit.

(astronomy) The small cluster of galaxies that contains the Milky Way Galaxy; includes Andromeda, Triangulum, the Large Magellanic Cloud, Small Magellanic Cloud and others.

(crystallography, mineralogy) The set of all symmetry operations that can be applied to a given crystal without changing it.

(chemistry) a vertical series of elements in the periodic table that have three valence electrons; boron is a metalloid, while aluminium, gallium, indium and thallium are metals

(chemistry) the vertical group of the periodic table containing carbon, silicon, germanium, tin and lead; the elements have a valence of 4, and show the typical gradation from nonmetal to metal

A group of people, sampled from a larger population, interviewed in open session for market research or political analysis.

(mathematics) A group of isometries leaving a fixed point.

A group of members of a political party or of a similar organisation who have decided to create their own organisation.

A collection of humans or animals who share certain characteristics, interact with one another, accept expectations and obligations as members of the group, and share a common identity.