What is the metric prefix for one millionth?

The metric prefix for one millionth is micro. In the metric system, the prefix "micro-" denotes a factor of 10^-6, which is equivalent to one millionth (1/1,000,000). This is commonly used in scientific measurements, such as micrometers (µm) and micrograms (µg), where precision is needed at very small scales.

The other prefixes provide different magnitudes: "milli-" represents one thousandth (10^-3), "centi-" stands for one hundredth (10^-2), and "kilo-" indicates one thousand (10^3). Understanding these prefixes is essential for interpreting and converting measurements in scientific contexts.