Impossible - Vine's Expository Dictionary of New Testament Words
Impossible
[ A-1,Adjective,G102, adunatos ]from a negative, and dunatos, able, strong," is used
(a) of persons, Acts 14:8, "impotent;" figuratively, Romans 15:1, "weak;"
(b) of things, "impossible," Matthew 19:26; Mark 10:27; Luke 18:27; Hebrews 6:4, Hebrews 6:18; Hebrews 10:4; Hebrews 11:6; in Romans 8:3, "for what the Law could not do," is, more lit., "the inability of the law;" the meaning may be either "the weakness of the Law," or "that which was impossible for the Law;" the latter is perhaps preferable; literalism is ruled out here, but the sense is that the Law could neither justify nor impart life.
[ A-2,Adjective,G418, anendektos ]
signifies "inadmissible" (a, negative, n, euphonic, and endechomai, "to admit, allow"), Luke 17:1, of occasions of stumbling, where the meaning is "it cannot be but that they will come."
[ B-1,Verb,G101, adunateo ]
signifies "to be impossible" (corresponding to A, No. 1), "unable;" in the NT it is used only of things, Matthew 17:20, "(nothing) shall be impossible (unto you);" Luke 1:37. AV "(with God nothing) shall be impossible;" RV, "(no word from God, a different construction in the best mss.) shall be void of power;" rhema may mean either "word" or "thing" (i.e., fact). In the Sept. the verb is always used of things and signifies either to be "impossible" or to be impotent, e.g., Genesis 18:14; Leviticus 25:35, "he fail;" Deuteronomy 17:8; Job 4:4, "feeble;" Job 42:2; Daniel 4:6; Zechariah 8:6.