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Two different characters that render almost identically, and which one you typed matters for search and sorting.
They look the same and are not the same. The micro sign is U+00B5 and is the SI prefix meaning one millionth; the Greek small letter mu is U+03BC and is a letter used for a coefficient of friction, a population mean, and much else. Text search, sorting and string comparison treat them as different characters, which is why a document can appear to contain a term it cannot find.
The micro sign and the Greek letter mu are different characters that render almost identically.
| Micro sign | Mu | |
|---|---|---|
| Code point | U+00B5 MICRO SIGN | U+03BC GREEK SMALL LETTER MU |
| What it means | The SI prefix micro, one millionth | A Greek letter used as a variable name |
| Where it belongs | Before a unit symbol: µm, µF, µSv | In an equation, as a quantity |
| Common substitution | A plain letter u where µ cannot be typed | Frequently typed in place of the micro sign |
| Relationship (from Symbolwise's records) | Commonly confused with Mu — The micro sign and the Greek letter mu are different characters that render almost identically. | Commonly confused with Micro sign — The SI prefix micro has its own character, U+00B5, separate from this Greek letter at U+03BC. They render almost identically and are substituted for each other constantly. |
Unicode Code Chart: Latin-1 Supplement (U+0080–U+00FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.
Unicode Code Chart: Greek and Coptic (U+0370–U+03FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.
Wikipedia · retrieved 2026-07-31
Tertiary reference. Used for origin narrative and for units the SI does not define, never for an official-definition claim.
Look for the horizontal line. Fire is a plain upward triangle; air is the same triangle with a bar drawn across its upper part. Dropping the bar is the commonest error in reproductions of the element set, and it turns air into fire.
The same rule as fire and air, inverted. Water is a plain downward triangle; earth is the same triangle with a bar across its lower part. The four element signs are one designed set: two point up, two point down, and within each pair the bar is the only difference.
Alpha is a Greek letter and stands for a quantity — an angle, a coefficient, a significance level. The proportionality sign is an operator and stands between two quantities to say they keep a constant ratio. The drawings differ in that the proportionality sign's right-hand stroke runs out in an open curve rather than closing into the letter's tail.
The becquerel counts nuclear decays — one per second — and says nothing about harm. The sievert weights absorbed energy by the kind of radiation delivering it, and so estimates biological effect. A becquerel of one isotope and a becquerel of another can carry very different risk, which is exactly why exposure limits and medical doses are stated in sieverts and never in becquerels.