(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.

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

(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.

(group theory) A group that has a presentation without relators; equivalently, a free product of some number of copies of ℤ.

(mathematics) Any discrete group of isometries of the hyperbolic plane.

(organic chemistry) Any chemical entity that is temporarily reacted with a functional group so as to protect it from a subsequent reaction

(chemistry) A functional group that is in close proximity to another that is taking part in a reaction; especially such a functional group that affects the rate or outcome of the reaction