From kategoros; to be a plaintiff, i.e. To charge with some offence -- accuse, object.

see GREEK kategoros

a. before a judge: absolutely (to make accusation), Acts 24:2, 19; τίνος, to accuse one, Matthew 12:10; Mark 3:2; Luke 6:7 T Tr text WH; R L Tr brackets; ; John 8:6; Acts 25:5; Acts 28:19; with the addition of a genitive of the thing of which one is accused (as Demosthenes 515 at the end): Acts 24:8; Acts 25:11 (unless it be thought preferable to regard the relative in these instances as in the genitive by attraction (so Buttmann, § 132, 16 at the end), since the common construction in Greek authors is κατηγόρουν τί τίνος, cf. Matthiae, § 370 Anm. 2, p. 849f, and § 378, p. 859; cf. Winer's Grammar, § 30, 9a.); τίνος περί τίνος, Acts 24:13 (Thucydides 8, 85; Xenophon, Hell. 1, 7, 2); with the genitive of person and accusative of the thing, Mark 15:3 (unless πολλά should be taken adverbially: much, vehemently); πόσα, Mark 15:4 L T Tr WH (Euripides, Or. 28); followed by κατά with the genitive of person, Luke 23:14 (Xenophon, Hell. 1, 7, 9 (cf. Winers Grammar, § 28, 1; p. 431 (402); Buttmann, § 132, 16)); passive to be accused (as 2 Macc. 10:13; Xenophon, Hell. 3, 5, 25; cf. Buttmann, § 134, 4): ὑπό τίνος, Matthew 27:12; Acts 22:30 L T Tr WH for Rec. παρά (τό τί κτλ., why (A. V. wherefore) he was accused; unless it is to be explained, what accusation was brought forward etc.); ὁ κατηγορούμενος, Acts 25:16.

b. of an extra-judicial accusation (Xenophon, mem. 1, 3, 4): absolutely, Romans 2:15; τίνος, John 5:45 (cf. Buttmann, 295 (254)); Revelation 12:10 R G Tr: solecistically τινα, Revelation 12:10 L T WH (cf. Buttmann, § 132, 16). [SYNONYMS: αἰτίασθαι, διαβάλλειν, ἐγκάλειν, ἐπικάλειν, κατηγορεῖν: αἰτίασθαι to accuse with primary reference to the ground of accusation (αἰτία), the crime; κατηγορεῖν to accuse formally and before a tribunal bring a charge against (κατά suggestive of animosity) publicly; ἐγκάλειν, to accuse with publicity (καλεῖν), but not necessarily formally or before a tribunal; ἐπικάλειν 'to cry out upon' suggestive of publicity and hostility; διαβάλλειν, properly, to make a verbal assault which reaches its goal (διά); in distinction from the words which allude to authorship (αἰτιάομαι), to judicial procedure (κατηγορέω), or to open averment (ἐγκαλέω, ἐπικαλέω), διαβάλλω expresses the giving currency to a damaging insinuation. διάβολος a secret and calumnious, in distinction from κατήγορος an open and formal, accuser. Schmidt, chapter 5.]