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.
corrective
The definition for corrective is "Intended to correct." Used in a sentence: The school decided to take corrective measures to prevent truancy.
curtail
The definition for curtail is "To make less." Used in a sentence: Doreen decided to curtail her spending after she bounced a check.
illuminate
The definition for illuminate is "To make clear." Used in a sentence: Her excellent lecture illuminated the complicated subject of nuclear physics.
repel
The definition for repel is "To resist, reject." Used in a sentence: The soldiers made a massive charge to repel the invaders.