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Micrometre (μm), sometimes written as "um" in limited character sets •
Ultrarapid metabolizer, a term used in pharmacogenomics to refer to individuals with substantially increased metabolic activity •
.um, the Internet domain for the US Minor Outlying Islands •
Um interface, the air interface for the GSM mobile telephone standard •
Unified Model, a global numerical weather prediction model •
User manual, a document or manual intended to give assistance to people using a particular system •
Utilization management, the evaluation of the appropriateness, medical need and efficiency of health care ==Other uses==