G1756
ἐνεργής, ἐναργής
effective
ἐνεργής, -ές (late form of ἐνεργός, on WH. cf. AR, Eph., 241), at work, active, effective: 1Co.16:9, Phm 6, Heb.4:12 (Cremer, 261).† (AS)
The KJV translates G1756 in the following manner:
effectual (4x), powerful (2x)
Full Thayer's lexicon entry
ἐνεργής — energḗs
ἐνεργής, ἐνεργες (equivalent to ἐνεργός, equivalent to ὁ ὤν ἐν τῷ ἔργῳ (English at work)), active: Heb 4:12; by a somewhat incongruous figuratively, in 1Co 16:9 a θύρα ἐνεργής is spoken of, 'an opportunity for the working of the gospel'; ἐνεργής γίνομαι ἐν τίνι, in something, Phm 1:6. ((Aristotle), Polybius, Diodorus, Plutarch, others.)
3 occurrences
I Corinthians (1), Philemon (1), Hebrews (1)