What prefix indicates one thousand of a base unit?

The prefix that indicates one thousand of a base unit is "kilo." This is derived from the metric system, where prefixes are used to denote multiples of ten. Specifically, "kilo" represents a factor of (10^3) or 1,000. For example, a kilogram (kg) is 1,000 grams, and a kilometer (km) is 1,000 meters. Understanding these prefixes is essential in the metric system as they help communicate measurements more effectively.

The other prefixes listed serve different purposes: "mega" represents one million (or (10^6)), "micro" denotes one-millionth (or (10^{-6})), and "hecto" signifies one hundred (or (10^2)). All of these have distinct values that do not equate to one thousand, which reinforces why "kilo" is the appropriate choice for this question.