* Mnemonic: This word comes from the Greek word "mnemonikos", meaning "relating to memory". The "m" before "ne" is silent.
* Pneumonia: This word comes from the Greek word "pneumon", meaning "lung". The "m" before "ne" is silent.
It's interesting to note that the "m" is not silent in the Greek words they come from. The silent "m" is a result of how the words were adopted into English.