Effectual - Vine's Expository Dictionary of New Testament Words
Effectual[ A-1,Adjective,G1756, energes ]
denotes active, powerful in action" (en, "in," ergon, "work;" Eng. "energy;" the word "work" is derived from the same root). It is translated "effectual" in 1 Corinthians 16:9, of the door opened for the Gospel in Ephesus, and made "effectual" in the results of entering it; and in Philemon 1:6, of the fellowship of Philemon's faith "in the knowledge of every good thing" (RV). In Hebrews 4:12 it describes the Word of God as "active," RV (AV, "powerful"), i.e., full of power to achieve results. See ACTIVE, POWERFUL.
[ B-1,Verb,G1754, energeo ]
"to put forth power, be operative, to work" (its usual meaning), is rendered by the verb "to work effectually," or "to be effectual," in the AV of 2 Corinthians 1:6; Galatians 2:8; 1 Thessalonians 2:13; in each case the RV translates it by the simple verb "to work" (past tense, "wrought"). In James 5:16 the RV omits the superfluous word "effectual," and translates the sentence "the supplication of a righteous man availeth much in its working," the verb being in the present participial form. Here the meaning may be "in its inworking," i.e., in the effect produced in the praying man, bringing him into line with the will of God, as in the case of Elijah. For a fuller treatment of the word, See WORK. See also DO, MIGHTY, SHEW, Note (11).
Note: The noun energeia, "working," is translated "effectual working," in the AV of Ephesians 3:7; Ephesians 4:16.