mystery

From Wiktionary

Pronunciation[change]

Noun[change]

Singular
mystery

Plural
mysteries

  1. (countable & uncountable) A mystery is a secret or hidden matter which can't be explained.
    She never told me where the money was, and it remains a mystery to me even now.
    She and her mystery man were seen outside her parents' home.
  2. (countable & uncountable) A mystery is a story about a puzzling event: short for mystery story.
    The police investigation has failed to solve the murder mystery.