The noun nonchalance means the state of being nonchalant or calm, showing the impression of not caring, lack of concern or disinterest in something.
Synonyms are apathy, casualness, disregard, or complacence.
The word origins from the French (13th century) nonchalance. It can be split in non- “not” + chaloir “have concern for”. The first recorded use was in 1678.
Adopting to his nonchalance was never easy, but you’ll get used to it someday.
He always has that nonchalance vibe when he’s studying. He doesn’t like to be distracted by anything.
This art work is too beautiful to be treated with nonchalance.