自願 的英文怎麼說?

[1] of one's own [accord or volition or (free) will][2] volunteer; voluntary; voluntarily[3] offer[4] by choice[5] on one's own will

of one's own volition 是正式或法律用語. [1]通常可以這麼用: One does something of one's own [accord/volition/(free) will]. [2][3]的用法是 One volunteers/offers to do something. 代表一個人自願做某事, 不過 offer 也可能指出價或提議. Voluntary 是形容詞.

自願也可以用 on one's own will，例如:

I went abroad to study on my own will. = 我自願出國念書