Contention signifies a conflict in words. Therefore, it can be understood in two ways since the one speaking sharpness is depraved in two ways. In one way, if through this one comes to favor what is false, as when someone, trusting in his loud voice, impugns the truth. In another way, on account of the disorder, as when sharpness is used either beyond the appropriate manner or against the character of the person. But if it be used moderately, both with due circumstances and for the truth, it is not a sin. And thus in rhetoric it is one instrument of exhortation. But in Sacred Scripture it is taken to mean the disorder.
[Thomas Aquinas, Commentaries on St. Paul's Epistles to Timothy, Titus, and Philemon, Baer, tr. St. Augustine's Press (South Bend, IN: 2007) p. 116.]