The definition for adversary is "One who opposes or resists." Used in a sentence: Franklin hoped to defeat his adversary in the afternoon's tennis match.

The definition for commemorate is "To mark by a ceremony." Used in a sentence: Each year, the Franklins commemorate their anniversary by visiting the site of their first date.

The definition for incumbent is "Necessary as a duty or responsibility." Used in a sentence: It was incumbent on Jack to attend his father's retirement party.

The definition for onset is "Beginning." Used in a sentence: Crocuses bloom at the onset of spring, sometimes even before the snow melts.

The definition for turpitude is "Essential baseness, depravity." Used in a sentence: The turpitude of the villain in the movie offended most audiences.