adversary
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.
exception
The definition for exception is "A case to which the rule does not apply." Used in a sentence: The teacher made an exception and let Gina eat her snack in class.
onset
The definition for onset is "Beginning." Used in a sentence: Crocuses bloom at the onset of spring, sometimes even before the snow melts.
opportune
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.
parity
The definition for parity is "Equality." Used in a sentence: Hilda, to avoid squabbles, aimed for parity in the slices of birthday cake.