amnesiac (noun) – a person who is suffering from partial or total loss of memory
BREAKDOWN: A- (no, without) + MNE- (memory) + -IAC (one who shows or suffers)
— amnesia is a partial or total loss of memory, due to shock or other psychological disturbance
This word is built on the root MNE-, which means memory or to remember.
Common MNE- words include amnesia.
More esoteric MNE- words include dysmnesia and mneme.