commemorate
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.
frugal
The definition for frugal is "Thrifty, cheap." Used in a sentence: The frugal shopper only bought items that were on sale.
futile
The definition for futile is "Without purpose, completely ineffective." Used in a sentence: Arguing with Andrew is futile because he never changes his mind.
implement
The definition for implement is "To carry out or accomplish." Used in a sentence: All Randolph needed to implement his plan was a moonless night and a long rope.
retroactive
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.