The 19th letter of the Greek alphabet.
The third flavour of charged lepton (in order of increasing mass), with electric charge -1.
Nineteenth letter (T, t), of Greek alphabet; any T-shaped thing.

Elementary particle with the same electric charge as the electron but a mass nearly double that of a proton. It has a lifetime of around 3 × 10-13 seconds and belongs to the lepton family of particles—those that interact via the electromagnetic, weak nuclear, and gravitational forces, but not the strong nuclear force.