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 compulsion is "An irresistible impulse." Used in a sentence: Tamar, a shoe fanatic, could not resist the compulsion to buy the shiny red boots.

The definition for finite is "Having definite limits." Used in a sentence: The exasperated mother had finite patience for her toddler's tantrums.

The definition for opportune is "Suitable or convenient." Used in a sentence: Quan stepped onto the platform at the most opportune time, just as the train pulled in.

The definition for trove is "Valuable collection." Used in a sentence: Walter's trove of vintage baseball cards was worth thousands of dollars.