Tau /ˈtɔː, ˈtaʊ/ (uppercase Τ, lowercase τ, or τ; Greek: ταυ [taf]) is the 19th letter of the Greek alphabet, representing the voiceless dental or alveolar plosive IPA: [t]. In the system of Greek numerals, it has a value of 300.
The K–Pg extinction event, brought on by an asteroid impact (Chicxulub impact) and possibly volcanism (Deccan Traps), marked the beginning of the Paleocene and killed off 75% of species, most famously the non-avian dinosaurs.