It is the name of a submultiple of the unit length meter, which until the late 1960s was called the micron, and is equivalent to its millionth part. That is why it is also called a micrometer, which is consistent with the rest of the multiples of the meter, but is confused with the tool. Its symbol is ? (micro), although it is sometimes replaced by the Greek letter 956; ( mi ) , which in many fonts are identical, but processors differentiate them.
