augment
The definition for augment is "To make greater." Used in a sentence: Wanda read the dictionary every night to augment her vocabulary.
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.
dubious
The definition for dubious is "Questionable." Used in a sentence: Karl found Kevin's claim that he was sick dubious, as he had just seen him playing football.
fidelity
The definition for fidelity is "State of being faithful." Used in a sentence: Unlike her fickle friend Benji, May Belle was known for her fidelity.
ploy
The definition for ploy is "A contrived plan." Used in a sentence: Sarah thought George's ploy of borrowing her notes was a cowardly way to ask her out.