What is the prefix meaning one one thousandth (1/1,000)?

The prefix that signifies one one thousandth (1/1,000) is "milli." This prefix is widely used in the metric system, where it indicates a division of the base unit by 1,000. For example, a millimeter is one one-thousandth of a meter, and a milliliter is one one-thousandth of a liter. The use of "milli" helps in precise measurement and is essential in fields such as electrical engineering, where small measurements are common.

The other options represent different metric prefixes: "deci" refers to one-tenth (1/10), "cent" denotes one hundredth (1/100), and "micro" indicates one millionth (1/1,000,000). Each of these prefixes serves its own function, but when specifically looking for the value of one one-thousandth, "milli" is the accurate choice.