Which prefix means "opposite of or against"?

The prefix "contra" comes from Latin and means "against" or "opposite of." It is often used in words to indicate a position that contradicts or opposes something. For example, "contradict" means to speak against, and "contrary" refers to something that is opposite. This prefix clearly conveys the idea of being contrary or in opposition to another concept or idea, which aligns perfectly with the question.

In contrast, the prefix "co" signifies together or with, suggesting collaboration rather than opposition. The prefix "non" indicates negation, meaning not or without, but it does not imply direct opposition. The prefix "dis" can mean apart, as in "disagree," which does suggest opposition but does not carry the same direct implication of contrast as "contra" does. Thus, "contra" is the most accurate choice for meaning "opposite of or against."