T-number or T number may refer to:
A numerical system for the glyphs within the Pre-Columbian Mayan script, see J. Eric S. Thompson. Dvorak technique, a system to subjectively estimate tropical cyclone intensity Viral capsid T-number, a system to describe the icosahedral surface quasi-symmetry pattern In music, the transposition of a tone row In number theory, a transcendental number having finite, but unbounded, transcendence measure. T-number (photography), a transmission aperture value in photography