Micro-


Micro is a unit prefix in the metric system denoting a factor of one millionth. It comes from the Greek word μικρός, meaning "small".
It is the only SI prefix which uses a character not from the Latin alphabet. In Unicode, the symbol is represented by or the legacy symbol. The prefix "mc" is also commonly used; for example, "mcg" denotes a microgram.

Examples

The official symbol for the SI prefix micro is a Greek lowercase mu. For reasons stemming from its design, Unicode has two different character codes for the letter, with slightly different appearance in some computer fonts, although most fonts use the same glyph. is in the Greek range. According to The Unicode Consortium, the Greek letter character is preferred, but implementations must recognize the micro sign as well, for compatibility with legacy character sets. This distinction also occurs in some legacy code pages, notably Windows-1253.
In circumstances in which only the Latin alphabet is available, ISO 2955, DIN 66030 and BS 6430 allow the prefix μ to be substituted by the letter as, for example, in um for μm, or uF for μF
Similarly, capacitor values according to the RKM code defined in IEC 60062 can be written as 4u7 instead of 4μ7 if the Greek letter μ is not available.
The CJK Compatibility block contains square forms of some Japanese katakana measure and currency units.
corresponds to マイクロ.

Other abbreviating conventions

In some health care institutions, house rules deprecate the standard symbol for microgram, "μg", in prescribing or chart recording, because of the risk of giving an incorrect dose because of the misreading of poor handwriting. The two alternatives are to abbreviate as "mcg" or to write out "microgram" in full. The alternative abbreviation may be ambiguous in rare circumstances in that mcg could also be read as a micrigram, i.e. 10−14 g; however the prefix micri is not standard, nor widely known, and is considered obsolete. This deprecation, focused on avoiding incorrect dosing in contexts where handwriting is often present, does not extend to all health-care contexts and institutions, and in physical sciences research, "μg" remains the sole official abbreviation.
In medical data exchange according to the Health Level 7 standard, the μ can be replaced by u as well.