Final answer:
The prefix that signifies multiplication by 1000 is 'kilo-'. For instance, 1 kilometer (km) is 1000 meters, and 1 kilogram (kg) is 1000 grams.
Step-by-step explanation:
The prefix that is added to the base unit to mean times 1000 is kilo-.
In the International System of Units (SI), multipliers such as prefixes are used to create larger or smaller units from the base unit, simplifying the representation of very large or very small quantities. The kilo- prefix indicates multiplication of the base unit by 1,000. For example, 1 kilometer (km) is equal to 1,000 meters, and 1 kilogram (kg) is equal to 1,000 grams. SI prefixes like kilo- are part of a system based on powers of ten, which makes conversions and calculations with different units more convenient.