expression, noun
one's own volition; one's own will
A formal phrase emphasizing that an action is taken by one's own free will, not under compulsion. Often used in legal or official contexts.
彼は自己の意思でその契約を結んだ。
He entered into the contract of his own volition.
自己の意思に基づいて行動することが大切だ。
It is important to act based on one's own will.
Compound of 自己 (self) + の (possessive particle) + 意思 (will, intention). The phrase is a straightforward combination of these elements.