complaint (a statement that you are not happy or satisfied with something): You should deal with customer complaints in a friendly manner.
grievance formal (a reason for complaint, especially unjust or unfair treatment): If you have a grievance, you may go to my superiors.
protest (a complaint expressing strong disagreement or disapproval of something): The organization has made a formal protest against the lack of food in the area.
gripe informal (a complaint, especially an unimportant one): Students’ only gripe is the poor quality of the dorm food.
