- pH
- 1909, from Ger. PH, introduced by S.P.L. Sörensen, from P, for Ger. Potenz "potency, power" + H, symbol for the hydrogen ion that determines acidity or alkalinity.
- ph
- consonantal digraph, now usually representing "f," originally the combination used by Romans to represent Gk. letter phi (cognate with Skt. -bh-, Gmc. -b-), which at first was an aspirated "p," later the same sound as Ger. -pf-, but by 2c. B.C.E. had become a simple sound made by blowing through the lips (bilabial spirant). Roman "f," like modern Eng. "f," was dentilabial; by c.400, however, the sounds had become identical and in some Romanic languages (It., Sp.), -ph- regularly was replaced by -f-. This tendency took hold in O.Fr. and M.E., but with the revival of classical learning the words subsequently were altered back to -ph- (except fancy and fantastic), and due to zealousness in this some non-Gk. words in -f- began to appear in -ph-, though these forms generally have not survived.