Donald J. Trump went Thursday night where Donald J. Trump, the candidate, seemed to have never gone before: He expressed broad regret about some of his caustic language during the campaign.

Precisely which words does Mr. Trump regret? He did not specify. But his speech in Charlotte, N.C., his third using a teleprompter this week, was praised by some of his critics as the best of his campaign.

“Sometimes, in the heat of debate and speaking on a multitude of issues, you don’t choose the right words or you say the wrong thing,” Mr. Trump said. “I have done that, and I regret it, particularly where it may have caused personal pain. Too much is at stake for us to be consumed with these issues.”

Mr. Trump has prided himself on never acknowledging regret, even when he attacked the parents of a fallen American Muslim soldier after they criticized him at the Democratic National Convention. “But one thing I can promise you is this: I will always tell you the truth,” he added.