Brewer's: Tertium Quid

A third party which shall be nameless. The expression originated with Pythagoras, who, defining bipeds, said -

?Sunt bipes homo, et avis, et tertium quid.?

?A man is a biped, so is a bird, and a third thing (which shall be nameless).?

Iamblichus says this third thing was Pythagoras himself. (Vita Pyth., cxxvii.) In chemistry, when two substances chemically unite, the new substance is called a tertium quid, as a neutral salt produced by the mixture of an acid and alkali.

Related Content Allusions Foreign Words and Phrases Latin and Greek Word Elements Names: Their Origins and Meanings Old Testament Names Mythology Ancient Greek Literature & Mythology The Bible (King James version) The Koran (translation by J. M. Rodwell) Shakespeare's Plays Tales from Shakespeare (Charles and Mary Lamb) Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language