A number of things or persons being in some relation to one another.
A set with an associative binary operation, under which there exists an identity element, and such that each element has an inverse.
An effective divisor on a curve.
A (usually small) group of people who perform music together.
A small number (up to about fifty) of galaxies that are near each other.
A column in the periodic table of chemical elements.
A functional group.
A subset of a culture or of a society.
An air force formation.
A collection of formations or rock strata.
A number of users with the same rights with respect to accession, modification, and execution of files, computers and peripherals.
An element of an espresso machine from which hot water pours into the portafilter.
A number of eighth, sixteenth, etc., notes joined at the stems; sometimes rather indefinitely applied to any ornament made up of a few short notes.
A set of teams playing each other in the same division, while not during the same period playing any teams that belong to other sets in the division.
A commercial organization.