Group - Definition and Overview

The term group can refer to several concepts:

• In music, a group is another term for band or other musical ensemble.
• In mathematics, a group is a set together with a binary operation satisfying certain algebraic conditions. See group (mathematics) as well as group theory.
• In astronomy, a group is a small number of galaxies (up to 50 or so) that are near each other, like the Local Group, which is the group of galaxies we live in. See groups and clusters of galaxies.
• In chemistry, a group is either
  • a column in the periodic table of chemical elements: see periodic table group; or
  • a functional entity consisting of certain atoms whose presence provides a certain property to a molecule, e.g. the methyl group; see Functional group.
• In sociology, a group involves a sub-set of a culture or of a society: see group (sociology).
• In the military, a group is an air force formation: see group (air force unit)
• In the Unix operating system each user belongs to at least one group. Each file belongs to one, and only one group: see Group identifier (Unix)
• In geology, a group is a collection of formations, or rock strata.