(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

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

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

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

In chemistry, a group of elements with related properties similar to that of platinum, notably high resistance to chemical activity, particularly oxidation and reaction with acids. The platinum group consists of the elements ruthenium, rhodium, palladium, osmium, iridium, and platinum. In the periodic table of the elements they are in period 5 or 6 and in groups 8, 9 or 10.

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

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

An algebraist who specializes in group theory

(US, Canada) A collection of residents representing a geographic or otherwise connected residential or business area who together ensure that their communities development interests are known, represented and supported.

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