IPA: /bɪˈliːvər/
KK: /bɪˈliːvər/
A person who has faith in something, especially in a religious belief.
She is a strong believer in the power of kindness.
Believer → It is formed from "believe" (from Old English "geliefan", meaning to have faith or trust) and "-er" (meaning a person who). A believer is a person who has faith or trust in something.
Think of someone who 'has faith' ('believe') — the '-er' just means a person. A believer is someone who has faith.