Which Greek prefix means "half"?

The Greek prefix that means "half" is indeed "hemi-." This prefix is derived from the Greek word "hēmi," which translates to "half." It is commonly used in various terms in the English language, such as "hemisphere," which refers to half of a spherical object like the Earth, and "hemiplegia," which denotes paralysis of one side of the body.

In contrast, the other prefixes listed have different meanings. "Amphi-" translates to "both" or "on both sides," indicating a dual nature. "Macro-" refers to something large or extensive, while "micro-" denotes something small or miniature in scale. Understanding these distinctions between prefixes helps clarify their usage in various contexts, particularly in scientific, medical, and academic vocabulary. Therefore, "hemi-" is the correct answer as it accurately aligns with the definition of "half."