Vain — adjective.
The word vain often appears in expressions such as in vain, meaning "without achieving anything" or "unsuccessfully."
“They tried in vain to save the building from the fire.”
Vain can also describe a person who is overly concerned with their looks or achievements.
“He’s so vain – he checks his reflection every few minutes.”
Author’s summary: The word “vain” describes both failure in achieving results and excessive self-admiration, depending on the context of use.