Which of the following prefixes indicates opposition?

The prefix "contra-" signifies opposition or contrast. This prefix is derived from Latin, where it means "against" or "opposite." It is used in various medical terms to indicate something that is counter to or opposing another condition or action. For instance, the term "contraceptive" refers to methods that work against conception, i.e., preventing pregnancy.

Other prefixes, while they may suggest negation or alteration, do not specifically convey the notion of opposition. "De-" typically indicates removal or reversal, as in "dehydrate," meaning to remove water. "Dis-" usually denotes separation or the negation of something, such as in "dislocate," referring to the separation of a joint. "Dys-" implies difficulty or abnormality, as seen in "dysfunction," meaning impaired function. Each of these prefixes carries its unique meaning, but only "contra-" clearly encapsulates the idea of opposition.