noun
written opinion; opinion in writing; argument
A formal document or statement expressing one's views, often submitted to an organization, court, or public body.
弁護士が裁判所に意見書を提出した。
The lawyer submitted a written opinion to the court.
市民から市長に意見書が送られた。
A written opinion was sent from a citizen to the mayor.
声明書 is a written statement or declaration, often public and formal, whereas 意見書 focuses on expressing an opinion or argument.
Compound of 意見 (opinion) and 書 (document, writing).