The definition for compulsion is "An irresistible impulse." Used in a sentence: Tamar, a shoe fanatic, could not resist the compulsion to buy the shiny red boots.

The definition for diffident is "Lacking self–confidence." Used in a sentence: The diffident student never raised her hand in class, even when she knew the answer.

The definition for placebo is "An inactive substance used in medical testing." Used in a sentence: Tom, who had taken the placebo, found that his allergy symptoms did not go away.

The definition for rehash is "To discuss again." Used in a sentence: "Sandra," said her mother, "I am tired of rehashing this same topic over and over."

The definition for stern is "Harsh, severe." Used in a sentence: The stern principal canceled the prom after the seniors played a silly prank.