noun
disagreement; disapproval; objection; dissent; non-consent
Formal term for lack of agreement, often used in legal, business, or official contexts. Can imply active refusal to consent.
彼の提案に不同意を表明した。
I expressed my disagreement with his proposal.
契約の変更には双方の同
Changes to the contract require mutual consent; if there is non-consent, they become void.
反対 is a more general and common word for opposition, while 不同意 is more formal and often used in specific contexts like legal or official disagreement.
Compound of 不 (fu, 'not') and 同意 (dōi, 'agreement, consent'). The word follows a standard Sino-Japanese pattern for negation.