Micro (Greek letter μ, mu, non-Italic type) is a metric prefix in the metric system denoting a factor of one millionth (10−6).["MICR,"
]
Accessed 10/13/2024.
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 .
When Greek alphabet characters are not available, the letter "u" is sometimes used instead of "μ". The prefix "mc" is also commonly used; for example, "mcg" denotes a microgram.
Examples
-
Typical bacteria are 1 to 10 μm in diameter.
-
Human hair typically varies in diameter from 17 to 181 μm.
-
Eukaryote are typically 10 to 100 μm in diameter.
[ Biology by Campbell & Reece, tenth edition. Ch. 6 "A Tour of the Cell". p. 98.]
Symbol encoding in character sets
The official symbol for the
metric prefix micro is a Greek lowercase mu (μ).
[ Prefixes of the International System of Units, International Bureau of Weights and Measures (page visited on 9 May 2016).] For reasons stemming from its design,
Unicode has two different character codes for the letter, with slightly different appearance in some fonts, although most fonts use the same glyph. () is in the "Latin-1 Supplement" range identical to ISO/IEC 8859-1 (since 1987),
[(Unicode 1.0, 1991)] residing at this code point also in
DEC MCS (since 1983) and ECMA-94 (since 1985). () is in the Greek range. According to The Unicode Consortium, the Greek letter character is preferred,
[ Unicode Technical Report #25] 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 (since 1974,[ [3]]), DIN 66030 (since 1980
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 (see also List of abbreviations used in medical prescriptions). 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 (for example, some clinical laboratories' reports adhere to it, whereas others do not
), and in physical sciences research, "μg" remains the sole official abbreviation.
In medical data exchange according to the Health Level 7 (HL7) standard, the μ can be replaced by u as well.
See also
