Strangely enough, there are three words frequently encountered in medical school that feature the pronunciation n[?]-’mä-nik (where [?] signifies a sometimes-varying vowel sound) and contain a silent consonant. Though they are frequently confused, each word is different, as is each silent consonant. A quick guide, including a mnemonic to keep them straight:
mnemonic: a memory aid. M is for Memory.
pneumonic: relating to the lungs; e.g. pneumonic plague. P is for Pulmonary (or Plague).
pathognomonic: definitively characteristic of a particular disease. G is for Guess (what you don’t have to do if you see a pathognomonic sign).
(gnomonic: a kind of map projection; not likely to be found in medical school.)