certain reasons; circumstances beyond explanation; adult matters
Used as a euphemism when the real reason cannot be disclosed, often implying professional, social, or personal constraints. Literally 'adult circumstances'.
The plan was canceled due to certain circumstances.
I can't go into details, but there are certain reasons.
Standard kanji spelling.
Katakana spelling sometimes used for stylistic emphasis or in informal contexts.
A set phrase combining 大人 (adult) and 事情 (circumstances). The exact origin is uncertain, but it is a modern euphemism for undisclosable reasons.