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.
beneficial
The definition for beneficial is "Helpful." Used in a sentence: there is no doubt that eating vegetables is beneficial to one's health.
elate
The definition for elate is "To fill with joy." Used in a sentence: It elated Margaret to be awarded first place in the science fair.
lurid
The definition for lurid is "Causing horror, shocking." Used in a sentence: The lurid photos of the crime scene upset the jury.
periodic
The definition for periodic is "Occurring at regular intervals." Used in a sentence: The periodic innterruptions of the cuckoo clock prevented Li from concentrating.