(linear algebra) An identity matrix

Any standardized, reproducible unit that can be used to measure any physical property.

(chemistry) The basic structural unit of a polymer; the monomer unit which has been polymerized.

Any division of quantity accepted as a standard of measurement or exchange; a unit of measure.

(cinematography) A separate team that shoots footage that is of secondary importance for the final cut of the motion picture, as opposed to first unit.

(cinematography) The team that shoots footage which is of primary importance for the final cut of the motion picture, including all scenes involving actors, or at least stars of the motion picture.

(US) any unit of measurement that is currently used in the United States / any traditional unit of measurement that is used by custom

(chemistry) A specific arrangement of atoms that repeats within a macromolecule / (genetics) A specific sequence of bases that repeats within a nucleic acid (or of amino acids within a protein)

(anatomy) The structure consisting of hair, hair follicle, arrector pili muscle and sebaceous gland.

(geometry) A circle of radius 1. / (trigonometry, the unit circle) The circle of radius 1 with centre at the origin, used in defining trigonometric functions.