What prefix means "against" or "opposite of"?

The prefix that means "against" or "opposite of" is commonly recognized as "anti-." This prefix is derived from Greek and is frequently used in medical terminology to describe substances, actions, or conditions that counteract or oppose something else. For example, when discussing "antibiotics," it refers to substances that work against bacteria.

In contrast, the other prefixes do not convey the same meaning. "Brady-" refers to something slow, "endo-" pertains to within or inside, and "non-" signifies not or absence of something. Understanding these prefixes helps in recognizing their usage in medical terms, enhancing comprehension of the language used in healthcare.