| Term | Definition |
| contraband | anything that is against the law to buy or sell |
| contradict | to express the opposite |
| contrarian | a person who thinks differently from other people; a person who does the opposite of what is expected |
| contrary | – completely different; opposite in nature, opinion, or action |
| contrast | to look at different things to see how they are opposites or not related |
| counterbalance | a weight used to balance an opposite weight |
| counterclockwise | in the direction that is opposite in movement of the directions on the hands on a clock |
| counterexample | an example used to support a claim or statement that is the opposite of another claim or statement |
| counterfeit | being the opposite of real; fake or artificial |
| counterintuitive | goes against your gut feeling or common sense |