um
Abbreviation with 7 meanings
| Stands for | Micrometer (micron) |
|---|---|
| Meanings | 7 |
| Categories | Units & Measurements, Business & Finance, Education & Academia, Medical, Geography & Places |
| Also written | UM |
um has seven meanings. The most common are Micrometer (micron) (metric and SI unit) and Uninsured motorist coverage (insurance); it can also stand for University of Michigan, Utilization management, U.S. Minor Outlying Islands, University of Miami and University of Mississippi.
Meanings of um at a glance
| # | um stands for | Context |
|---|---|---|
| 1 | Micrometer (micron) | Units & Measurements › Metric and SI Unit |
| 2 | Uninsured motorist coverage | Business & Finance › Insurance |
| 3 | University of Michigan | Education & Academia › University |
| 4 | Utilization management | Medical › Hospital |
| 5 | U.S. Minor Outlying Islands | Geography & Places › US Territory and Military Mail |
| 6 | University of Miami | Education & Academia › University |
| 7 | University of Mississippi | Education & Academia › University |
1. Micrometer (micron)
Units & Measurements · Metric and SI Unit Abbreviations
One millionth of a meter, properly written μm with the Greek letter mu; um is the plain-text substitute used where that character is unavailable. It measures cells, bacteria, dust particles, fiber diameters and filter ratings.
Example: The HEPA filter captures 99.97 percent of particles 0.3 um in diameter.
The older name micron (symbol μ) was officially dropped from SI in 1967 but remains common in filtration, coatings and semiconductor work. A human hair is roughly 50 to 100 um thick, and PM2.5 air pollution refers to particles 2.5 um across or smaller. Medicine replaces μ with mc, as in mcg, to prevent misreading. A micrometer is also a precision screw gauge used by machinists.
2. Uninsured motorist coverage (UM)
Business & Finance · Insurance Abbreviations · also used in transportation
Auto insurance that pays for injuries to the policyholder and passengers, and in some states vehicle damage, when the at-fault driver has no liability insurance or in a hit-and-run.
Example: The hit-and-run driver was never found, so my UM coverage paid for my physical therapy.
Insurance Research Council estimates suggest that roughly one in seven US drivers is uninsured, which is why many states require insurers to offer UM coverage. It is usually sold together with underinsured motorist coverage (UIM), and limits often match the policy's own liability limits.
3. University of Michigan (UM)
Education & Academia · University Abbreviations
Flagship university of Michigan, founded in Detroit in 1817 and moved to Ann Arbor in 1837, a leading public research university with one of the largest research budgets in the country. Its Wolverines play in the Big Ten at Michigan Stadium, the largest stadium in the US.
Example: She was admitted to UM's Ross School of Business as a freshman.
The university prefers "U-M" or "UMich" to avoid confusion with the University of Miami, the University of Maryland, the University of Mississippi and others that use UM. Michigan Stadium, "the Big House", seats more than 107,000. The Peace Corps was proposed by John F. Kennedy in a 1960 speech on its campus.
4. Utilization management (UM)
Medical · Hospital Abbreviations
Broader system by which insurers and health organizations manage the appropriateness and cost of care, including prior authorization, concurrent review and retrospective review.
Example: UM nurse requested clinical update for day 4 of stay.
Prior authorization is the part of UM most visible to patients and clinicians. Federal rules finalized in 2024 require many health plans to speed up and report on prior authorization decisions. UM differs from case management, which focuses on coordinating care for individuals.
5. U.S. Minor Outlying Islands (UM)
Geography & Places · US Territory and Military Mail Abbreviations
ISO code grouping nine small US island territories: Baker, Howland and Jarvis islands, Johnston Atoll, Kingman Reef, Midway Atoll, Navassa Island, Palmyra Atoll and Wake Island. None has a permanent population, and UM is not a USPS state code, so it appears in data rather than on envelopes.
Example: The dataset tags Midway Atoll with the code UM rather than US.
UM shows up in country drop-down menus, statistics and software locale lists because ISO 3166-1 treats the islands as a separate entry with alpha-3 UMI. Mail to Wake or Midway moves through military or contractor channels. UM also abbreviates the University of Michigan and the University of Miami.
6. University of Miami (UM)
Education & Academia · University Abbreviations
Founded in 1925 in Coral Gables, Florida, the private university is known for its marine and atmospheric science school, medical center and Hurricanes athletics in the ACC. Its football team won five national titles between 1983 and 2001.
Example: She is studying marine biology at UM's Rosenstiel School on Virginia Key.
The university commonly uses "UM" or "the U", while the University of Michigan prefers "U-M". The Miller School of Medicine partners with Jackson Memorial Hospital. Its mascot is Sebastian the Ibis.
7. University of Mississippi (UM)
Education & Academia · University Abbreviations
Mississippi's flagship public university in Oxford, founded in 1848 and widely known as Ole Miss. In 1962 James Meredith became its first Black student after federal marshals and troops enforced a court order.
Example: UM's Croft Institute offers a demanding international studies program.
The university uses both "UM" and "Ole Miss", the latter a 19th-century yearbook name. Its Rebels compete in the SEC. William Faulkner's home, Rowan Oak, is owned by the university.
Related abbreviations
More metric and SI unit abbreviations
- a – Atto- (quintillionth)
- amu – Atomic mass unit
- AU – Astronomical unit
- Bq – Becquerel
- c – Centi- (hundredth)
- CBM – Cubic meter (freight)
- cc – Cubic centimeter
- cd – Candela
See all 64 metric and SI unit abbreviations →
More insurance abbreviations
- TPFT – Third party, fire and theft
- UBI – Usage-based insurance
- UIM – Underinsured motorist coverage
- UL – Universal life insurance
- UW – Underwriting
- VUL – Variable universal life
- WC – Workers' compensation
- WL – Whole life insurance
See all 86 insurance abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.