A group of people who identify with one another, especially on the basis of ancestral, national, cultural, historical or religious grounds.

(physics) the propagation velocity of the envelope of a modulated travelling wave, which is considered as the propagation velocity of information or energy contained in it.

(mathematics) the set of rigid motions that are also affine transformations.

(mathematics) The group of all affine transformations of a finite-dimensional vector space.

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