mm
Abbreviation with 11 meanings
| Stands for | Millimeter |
|---|---|
| Meanings | 11 |
| Categories | Units & Measurements, Medical, Geography & Places, Education & Academia, Military, Writing & Everyday, Religion |
| Also written | MM, mM |
mm has 11 meanings. The most common are Millimeter (metric and SI unit) and Malignant melanoma (dermatology); it can also stand for Multiple myeloma, Million (from Roman numerals MM), Month (two-digit, in date formats), Myanmar and Millimolar, plus 4 more listed below.
Meanings of mm at a glance
| # | mm stands for | Context |
|---|---|---|
| 1 | Millimeter | Units & Measurements › Metric and SI Unit |
| 2 | Malignant melanoma | Medical › Dermatology |
| 3 | Multiple myeloma | Medical › Hematology and Oncology |
| 4 | Million (from Roman numerals MM) | Units & Measurements › Math |
| 5 | Month (two-digit, in date formats) | Units & Measurements › Time |
| 6 | Myanmar | Geography & Places › Country Code |
| 7 | Millimolar | Units & Measurements › Metric and SI Unit |
| 8 | Master of Music | Education & Academia › Degree |
| 9 | Machinist's Mate | Military › US Navy and Coast Guard Rating |
| 10 | Misplaced modifier | Writing & Everyday › Proofreading and Correction Mark |
| 11 | Maryknoll (Catholic Foreign Mission Society of America) | Religion › Religious Title |
1. Millimeter
Units & Measurements · Metric and SI Unit Abbreviations
A thousandth of a meter, about 0.039 inch, used for precise dimensions in engineering drawings, rainfall totals, camera lenses, fasteners, jewelry and screen sizes in metric countries.
Example: The bolt is M8, meaning an 8 mm nominal diameter, with a 1.25 mm thread pitch.
Metric engineering drawings are dimensioned in mm by default, often with no unit written at all. Film and sensor formats (35 mm, 16 mm) and lens focal lengths (50 mm) use it even in the US. Rainfall of 25.4 mm equals one inch. Capitalization matters: Mm would be a megameter, a million meters, and MM is shorthand for million or a two-digit month.
2. Malignant melanoma (MM)
Medical · Dermatology Abbreviations
Cancer of the pigment-producing melanocytes, the deadliest common skin cancer because it can spread early to lymph nodes and distant organs. Warning signs include a new or changing mole that is asymmetric, irregularly bordered, multicolored or larger than a pencil eraser.
Example: Excision: superficial spreading MM, Breslow depth 1.2 mm, no ulceration; sentinel node biopsy recommended.
Prognosis depends most on Breslow thickness, the depth measured in millimeters, introduced by Alexander Breslow in 1970. Immune checkpoint inhibitors approved from 2011 onward transformed survival for advanced disease. Intermittent intense sun exposure and blistering sunburns, especially in childhood, raise risk. In hematology MM means multiple myeloma, so oncology notes generally write "melanoma".
3. Multiple myeloma (MM)
Medical · Hematology and Oncology Abbreviations
Cancer of plasma cells in the bone marrow that produces abnormal antibodies, causing bone lesions and fractures, anemia, kidney damage, high calcium and infections. It is the second most common blood cancer in the US and is about twice as common in Black Americans.
Example: Newly diagnosed MM, IgG kappa, R-ISS stage II; starting daratumumab-VRd, transplant candidate.
Diagnosis follows the International Myeloma Working Group criteria, updated in 2014 to include biomarkers of high risk (SLiM criteria) alongside CRAB features. Treatment has advanced rapidly with proteasome inhibitors, immunomodulatory drugs, anti-CD38 antibodies, autologous stem cell transplant, CAR-T cell therapy and bispecific antibodies, and median survival now exceeds several years. In some settings MM is short for millimeter, though mm is standard.
4. Million (from Roman numerals MM) (MM)
Units & Measurements · Math Abbreviations
Financial, banking and oil-and-gas shorthand for million, built from two Roman-numeral thousands (a thousand thousands). It appears in deal sizes, budgets and production figures such as $10MM or 5 MMbbl.
Example: The fund closed at $250MM in commitments from institutional investors.
Used where M already means thousand, so that $500M and $500MM can coexist in the same report. Investment bankers and private equity firms use it widely, although general readers may take it for a typo. MMBtu (million British thermal units) and MMcf (million cubic feet) follow the same pattern.
5. Month (two-digit, in date formats) (MM)
Units & Measurements · Time Abbreviations
Placeholder for a two-digit month, 01 to 12, in form instructions and software date patterns such as MM/DD/YYYY or YYYY-MM-DD. A single M usually means the month without a leading zero.
Example: Enter your card's expiration date in MM/YY format.
In many programming format strings case matters: MM means month while mm means minutes (Java, .NET and Unicode CLDR patterns), and MMM or MMMM give the abbreviated or full month name. Mixing up MM and mm is a classic bug that puts minutes where the month should be. Credit cards print expiration dates as MM/YY.
6. Myanmar (MM)
Geography & Places · Country Code Abbreviations
Myanmar, formerly Burma, received the code MM in 1989 when the military government changed the English name, replacing the old code BU. Naypyidaw has been the capital since 2006, while Yangon is the largest city.
Example: Humanitarian agencies track displacement figures for MM monthly.
The alpha-3 code is MMR. The language code my means Burmese, which can confuse developers, since MY is Malaysia. Many governments and media still use Burma.
7. Millimolar (mM)
Units & Measurements · Metric and SI Unit Abbreviations
One thousandth of a mole per liter, the concentration scale for buffers, salts and metabolites in biology and biochemistry. Blood sodium is about 140 mM, and many cell culture media contain 2 to 4 mM glutamine.
Example: Add MgCl2 to a final concentration of 2 mM in the PCR master mix.
Capitalization is essential: mM is millimolar, while mm is millimeter and MM is shorthand for million. Smaller concentrations use μM (micromolar, often typed uM) and nM (nanomolar), the range in which drug potency values such as IC50 are reported. Clinical laboratories usually write mmol/L instead.
8. Master of Music (MM)
Education & Academia · Degree Abbreviations
Graduate music degree in performance, composition, conducting, music education or theory, typically two years with recitals and juries. Admission depends mainly on an audition or portfolio, and many performers continue to a DMA or an artist diploma.
Example: He finished an MM in cello performance at Indiana's Jacobs School of Music.
Also written MMus (common in the UK and Canada) and M.M. A Master of Arts in music is usually more academic, focused on musicology or theory. MM also appears after the names of Maryknoll priests and brothers, a completely unrelated meaning.
9. Machinist's Mate (MM)
Military · US Navy and Coast Guard Rating Abbreviations
Sailors who operate and maintain propulsion turbines, pumps, compressors, refrigeration, air conditioning, steering gear and other mechanical systems. Nuclear-trained machinist's mates (MMN) run the steam plants of reactor-powered carriers and submarines.
Example: MM1 Ford supervised the main engine warm-up before getting underway.
Submarine machinist's mates also maintain atmosphere control and weapons-handling equipment, and a weapons specialty (MMW) handles torpedoes. The badge shows a three-bladed propeller. Nuclear MMs complete Nuclear Power School and prototype training, one of the Navy's most demanding pipelines.
10. Misplaced modifier (MM)
Writing & Everyday · Proofreading and Correction Mark Abbreviations
Flags a word or phrase positioned so that it seems to modify the wrong part of the sentence, as in "She served sandwiches to the children on paper plates."
Example: MM: "I only ate two cookies" should probably be "I ate only two cookies" in formal writing.
Limiting words such as "only," "just," "nearly" and "almost" are frequent culprits, because their position changes the meaning. Moving the modifier next to the word it describes usually solves the problem. Unlike a dangling modifier, a misplaced modifier does have a target in the sentence, just in the wrong place.
11. Maryknoll (Catholic Foreign Mission Society of America) (MM)
Religion · Religious Title Abbreviations
Maryknoll priests and brothers are members of the first US-founded Catholic missionary society, established in 1911 and headquartered in Ossining, New York. Separate Maryknoll congregations exist for sisters and lay missioners.
Example: The clinic in Tanzania was started by Fr. Edward Hayes, MM.
Maryknoll missioners have served in Asia, Africa and Latin America, and several were killed during conflicts, including four US churchwomen in El Salvador in 1980, two of whom were Maryknoll Sisters. Orbis Books is Maryknoll's publishing house. In music, MM can also mean metronome marking.
Related abbreviations
More metric and SI unit abbreviations
- mcg – Microgram
- mg – Milligram
- MKS – Meter-kilogram-second system
- mL – Milliliter
- mmol – Millimole
- mol – Mole
- mSv – Millisievert
- Mt – Megaton (TNT equivalent)
See all 64 metric and SI unit abbreviations →
More dermatology abbreviations
- LP – Lichen planus
- LS – Lichen sclerosus
- MCC – Merkel cell carcinoma
- MIS – Melanoma in situ
- MMS – Mohs micrographic surgery
- NB-UVB – Narrowband ultraviolet B phototherapy
- NMSC – Nonmelanoma skin cancer
- PASI – Psoriasis Area and Severity Index
See all 52 dermatology abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.