A demographic grouping based on age.

A group of people joined temporarily to accomplish some task or take part in some organised collective action. / (US military) A component of a naval task force.

(organic chemistry) A specific grouping of elements that is characteristic of a class of compounds, and determines some properties and reactions of that class.

Used other than figuratively or idiomatically: see group, theory; a theory about (particular kinds of) groups.

(mineralogy) A large group of silicate minerals having a silicon to oxygen ratio of 1:2. This group includes many silicates of sodium, potassium, calcium, and aluminum in an open network structure.

(group theory) The projective general linear group mathbf PGL(2,ℂ): the group of Möbius transformations on the Riemann sphere.

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.

(physics, mathematics) The group of all Lorentz transformations in spacetime.

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

(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