Non-SI metric units refer to metric units of measurement that are not part of the International System of Units (SI), which is the standardized system of measurement adopted worldwide. While the SI system is based on a set of base units (like meters for length, kilograms for mass, seconds for time, etc.), non-SI metric units include other units that may still be expressed in multiples and fractions of the base ten system but do not have official status within the SI framework.
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