Units of speed are always a unit of length per unit of time. Different units of length and time may be chosen depending on the situation. This makes it easier to read the measurements. For example ...

―Units of Length― Barky realizes that the measurement can be made by counting how many 1-centimeter items are needed, and the customer's foot is measured successfully. Transcript ...

A nanometer (nm) is a unit of length in the metric system, defined as one billionth (10-9) of a meter (m). The meter is the base unit of length in the International System of Units (SI), making the ...