beneficial
The definition for beneficial is "Helpful." Used in a sentence: there is no doubt that eating vegetables is beneficial to one's health.
corrosive
The definition for corrosive is "Bitingly sarcastic." Used in a sentence: The cruel Estella's corrosive comments made Pip cry.
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.
pantomime
The definition for pantomime is "Telling a story through gestures." Used in a sentence: The jealous actress called her understudy's performance a ridiculous pantomime.
pretentious
The definition for pretentious is "Making unjustified claims." Used in a sentence: The pretentious boy said that he was the fastest runner, but he finished last in the race.