A set of things sharing defining features; a category.

• Any grouping distinguished by common attributes.

A social stratum based on income, occupation, or status.

• The division of society into such strata.

A scheduled course or lesson in a subject.

• The group of students meeting regularly with a teacher.

A cohort that begins or finishes schooling in the same year.

A category of service or seat on transport, with a fare level.

A taxonomic rank below phylum and above order.

Elegance, style, or admirable quality.

• The best or highest standard.

To assign to a category; to classify.

• To be grouped or ranked.

In programming, a template defining objects with shared data and behavior.

In statistics, an interval grouping of data values.

• In set theory, a collection defined by a property, possibly a proper class.

Informal, chiefly British: excellent; impressive.