1. A unit of length equal to one millionth of a meter, or one thousandth of a millimeter; symbol: μm.
Usage: Also called micron in informal usage.; Standard metric unit used in science and engineering.
2. A precision instrument used to measure small distances or thicknesses, typically consisting of a calibrated screw mechanism.
Usage: Also called micrometer in U.S. English.; Common in engineering and laboratory settings.

Examples

• The thickness of the wire was measured at 50 micrometres.
• Bacteria are typically a few micrometres in diameter.
• The engineer used a micrometre to check the precision of the machined part.
• A human hair is roughly 70 micrometres thick.
• The micrometre reading showed a variation of only 0.01 mm.
• In microscopy, objects are often measured in micrometres.
• The micrometre screw must be turned carefully to avoid damaging the sample.