pn-
an initial combination occurring only in words from Greek; the p is usually mute in English.
(The p is pronounced in French, Spanish, Italian, German, Dutch, and other European langs.; also by Englishmen in reading Greek. It is to be desired that it were sounded in English also, at least in scientific and learned words; since the reduction of pneo- to neo-, pneu- to new-, and pnyx to nix, is a loss to etymology and intelligibility, and a weakening of the resources of the language.)