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to cross one's T's (and dot one's i's) "to be exact" is attested from 1849. Phrase to a T "exactly" is recorded from 1690s, though the exact signification is uncertain, despite much speculation. The measuring tool called a T-square is recorded by that name from 1785.
temperature (often italic)
The symbol for the isotope tritium.
absolute temperature (often italic)
tetanus toxoids vaccine
A technical foul: The ''T'' was absolutely ridiculous (1990s+ Basketball)