Micrometer (µm)
Definition: A micrometer (symbol: µm) is one millionth of a meter (0.000001 m or 10^-6 m). It is a metric unit used for very small distances.
History/origin: The micrometer became standard in science and engineering as microscopy, machining, and materials analysis advanced. It replaced older terminology such as the micron, which is still sometimes used informally.
Current use: Micrometers are used for cell sizes, bacteria, dust particles, textile fibers, thin coatings, and manufacturing tolerances in engineering and precision machining.
