Mark 12:3κενόν
But they seized the servant, beat him, and sent him away empty-handed.
Luke 1:53κενούς
He has filled the hungry with good things, but has sent the rich away empty.
Acts 4:25κενά
You spoke by the Holy Spirit through the mouth of Your servant, our father David: ‘Why do the nations rage and the peoples plot in vain?
1 Corinthians 15:10κενὴ
But by the grace of God I am what I am, and His grace to me was not in vain. No, I worked harder than all of them—yet not I, but the grace of God that was with me.
Philippians 2:16κενὸν
as you hold forth the word of life, in order that I may boast on the day of Christ that I did not run or labor in vain.
1 Thessalonians 3:5κενὸν
For this reason, when I could bear it no longer, I sent to find out about your faith, for fear that the tempter had somehow tempted you and that our labor might have been in vain.

Abbott-Smith

κενός, -ή, -όν
[in LXX chiefly for רִיק and cognate forms ;]
empty (Gen.37:24, Jdg.7:16). Metaphorical,

(a) empty, vain: λόγοι, Eph.5:6; ἀπάτη, Col.2:8; κήρυγμα, πίστις, 1Co.15:14;

(b) vain, fruitless: ἡ χάρις, 1Co.15:10; κόπος, 1Co.15:50; ἡ εἴσοδος, 1Th.2:1; κενά, Act.4:25 (LXX); εἰς κενόν, in vain, to no purpose (Diod., LXX; cl. διὰ κενῆς), 2Co.6:1, Gal.2:2, Php.2:16, 1Th.3:5;

(with) of persons, empty-handed: Mrk.12:3, Luk.1:53 20:10-11; vain, Jas.2:20.†
SYN.: μάταιος, of the aim or effect of an action, κ. of its quality (Lft. on Cl. Rom., 1Co., § 7; Tr., Syn., xlix)
(AS)

Sources: Abbott-Smith’s Manual Greek Lexicon of the New Testament (1922, public domain) and glosses from STEPBible TBESG (CC BY 4.0); STEPBible TAGNT (Greek New Testament, CC BY 4.0); the Berean Standard Bible (public domain). Reformatted by Word Study, wording unchanged. All sources and licenses.