mystery
n. C / Un. something that is difficult to understand or explain. It can also be a story or movie about a crime that is not solved until the end.
n. something that remains unexplained or unknown; a quality of being secretive or obscure. It also refers to a fictional genre focused on the investigation of a crime.
The cause of the fire is still a mystery.
She loves reading a good murder mystery before she goes to sleep at night.
The origins of the ancient ruins remain shrouded in mystery, as no written records from that civilization have ever been recovered by archaeologists.
From Middle English mysterie, from Anglo-Norman misterie (Old French mistere), from Latin mysterium, from Ancient Greek μυστήριον (mustḗrion, “a mystery, a secret, a secret rite”), from μύστης (mústēs, “initiated one”), from μυέω (muéō, “to initiate”), from μύω (múō, “to shut”). Displaced native Old English ġerȳne.
Countable when referring to a specific puzzle or story; uncountable when referring to the general quality of being unknown.