the nineteenth letter of the Greek alphabet (T, τ), transliterated as ‘t’ 希腊字母表中第十九个字母(译写为t) ■(Tau)[followed by Latin genitive](Astronomy)the nineteenth star in a constellation (天文)τ星(星座中第十九颗星) Tau Ceti. 鲸鱼座τ星。 ■(全称 tau particle 或 tau lepton)(Physics)an unstable subatomic particle of the lepton class, with a charge of -1 and a mass roughly 3,500 times that of the electron (物理)τ粒子