A.T. Robertson Commentary Titus 1:16

"They profess that they know God; but by their works they deny him, being abominable, and disobedient, and unto every good work reprobate." — Titus 1:16 (ASV)

They profess (ομολογουσιν). Present active indicative of ομολογεω, common verb (ομου, λεγω) as in Ro 10:10f. Ειδενα (know) is second perfect active infinitive of οιδα in indirect assertion.

By their works (τοις εργοις). Instrumental case.

They deny (αρνουντα). Present middle of αρνεομα, old verb, common in the Gospels and the Pastoral Epistles (1 Timothy 5:8; Titus 2:12; 2 Timothy 2:12).

Abominable (βδελυκτο). Verbal adjective from βδελυσσομα. Only in LXX and here.

Disobedient (απειθεις). See Ro 1:30.

Reprobate (αδοκιμο). See on 1 Corinthians 9:27; Romans 1:28.