The Greek adverb dōrean means 'freely,' 'as a gift,' 'gratis,' or 'without cause.' Derived from dōrea (G1431, 'a free gift'), it describes something given or done without payment, without obligation, or without merit on the recipient's part.
Romans 3:24 uses dōrean in one of the clearest statements of justification by grace: 'and all are justified freely by his grace through the redemption that came by Christ Jesus.' The adverb rules out any human contribution — the justification is a pure gift, given without charge.
Revelation 21:6 and 22:17 use dōrean in the eschatological invitation: 'To the thirsty I will give water without cost from the spring of the water of life.' The final invitation of Scripture uses this word: salvation, in its ultimate fullness, is freely given to all who come.