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 illuminate is "To make clear." Used in a sentence: Her excellent lecture illuminated the complicated subject of nuclear physics.

The definition for intricate is "Having complex and interrelated parts." Used in a sentence: The intricate poem baffled most readers with its numerous obscure metaphors.

The definition for retroactive is "effective as of a prior time or condition." Used in a sentence: The retroactive law made even past infractions punishable.

The definition for revive is "To bring back to life." Used in a sentence: Hank tried to revive Clare's interest in the project, but her enthusiasm had expired.