IPA: //ˌmɪθəˈmeɪniə//
KK: /mɪθəˈmeɪniə/
A strong tendency to lie or exaggerate, often to make stories more interesting or dramatic.
His mythomania made it difficult for his friends to trust anything he said.
Mythomania is formed from "mythos" (from Greek, meaning story or myth) and "mania" (from Greek, meaning madness or obsession). The word describes an obsession with or a compulsion to tell or believe in myths or falsehoods.
Think of 'myth' as a story and 'mania' as an obsession — this helps you remember that mythomania refers to an obsession with myths or untruths.