Willing, voluntary, or of one's own accord — the opposite of compulsion. Used in Romans 8:20 (creation subjected to frustration 'not of its own will') and 1 Corinthians 9:17 (Paul preaching 'voluntarily' merits reward).
The word hekōn opens profound questions about freedom, responsibility, and redemption. Romans 8:20 states that creation was subjected to futility 'not of its own will' (ouch hekousa) — the creation did not choose the fall, yet bears its consequences, and so groans for liberation. Paul in 1 Corinthians 9:17 reasons that willing obedience carries a weight that reluctant compliance does not. God loves a cheerful giver (2 Corinthians 9:7), and Paul's desire is that goodness be done willingly, not under compulsion (Philemon 14).