The definition for diffident is "Lacking self–confidence." Used in a sentence: The diffident student never raised her hand in class, even when she knew the answer.

The definition for impenitent is "Lacking remorse." Used in a sentence: The impenitent criminal received a harsh penalty, but his remorseful accomplice was released.

The definition for inviolable is "Secure from assault of trespass." Used in a sentence: Situated on a mountain, with sixteen–foot walls, the castle was inviolable.

The definition for melodious is "Having a pleasing melody." Used in a sentence: The melodious sounds of the symphony soothed Tim after his trying day.

The definition for repentant is "Feeling regret." Used in a sentence: The repentant Dana admitted to cheating on the test.