Толковый словарь английского языка - tau

noun Etymology: Middle English taw, from Latin ~, from Greek, of Semitic origin; akin to Hebrew tāw taw Date: 14th century the 19th letter of the Greek alphabet, a short-lived elementary particle of the lepton family that exists in positive and negative charge states and has a mass about 3500 times greater than an electron, a protein that binds to and regulates the assembly and stability of neuronal microtubules and that is found in an abnormal form as the major component of neurofibrillary tangles