genial
The definition for genial is "Sympathetic, friendly." Used in a sentence: The genial host warmly greeted his many guests.
placebo
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.
retroactive
The definition for retroactive is "effective as of a prior time or condition." Used in a sentence: The retroactive law made even past infractions punishable.
serenity
The definition for serenity is "Calmness." Used in a sentence: The serenity of the glassy sea soothed the sailors after the big storm.
turmoil
The definition for turmoil is "Extreme confusion, agitation." Used in a sentence: The windstorm caused such turmoil in the lake that the sailboat capsized.