Hubbry Logo
Micro-Micro-Main
Open search
Micro-
Community hub
Micro-
logo
7 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Contribute something
Micro-
Micro-
Micro-
View on Wikipedia
from Wikipedia

μ
Micro-
In UnicodeU+03BC μ GREEK SMALL LETTER MU
Different from
Different fromU+00B5 µ MICRO SIGN (discouraged)
Look up micro- in Wiktionary, the free dictionary.

Micro (Greek letter μ, mu, non-italic) is a unit prefix in the metric system denoting a factor of one millionth (10−6).[1] It comes from the Greek word μικρός (mikrós), meaning "small".[2]

It is the only SI prefix which uses a character not from the Latin alphabet. In Unicode, the symbol is represented by U+03BC μ GREEK SMALL LETTER MU or the legacy symbol U+00B5 µ MICRO SIGN. The prefix "mc" is also commonly used; for example, "mcg" denotes a microgram (whereas mg denotes a milligram).[3]

Examples

[edit]

Symbol encoding in character sets

[edit]

The official symbol for the SI prefix micro is a Greek lowercase mu (μ).[6] 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. U+03BC μ GREEK SMALL LETTER MU is in the Greek range. According to The Unicode Consortium, the Greek letter character is preferred,[7] 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In circumstances in which only the Latin alphabet is available, ISO 2955 (since 1974,[8] withdrawn 2001[9]), DIN 66030 (since 1980[10][11]) and BS 6430 (since 1983) allow the prefix μ to be substituted by the letter ⟨u⟩ (U+0075 u LATIN SMALL LETTER U) as, for example, in um for μm, or uF for μF . Similarly, capacitor values according to the RKM code defined in IEC 60062 (since 1952) can be written as 4u7 (or 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. U+3343 ㍃ SQUARE MAIKURO corresponds to マイクロ maikuro.

Other abbreviating conventions

[edit]

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.[12] The two alternatives are to abbreviate as "mcg"[12][3] 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[12]), 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.[13]

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Micro-

View on Grokipedia
from Grokipedia
Micro- is a prefix in the International System of Units (SI) that denotes a factor of one millionth, or 10^{-6}, of the base unit it modifies. It originates from the word mikrós (μικρός), meaning "small," and its corresponding symbol is the lowercase Greek letter mu (μ). This prefix is used across scientific and technical fields to express very small measurements, such as in the micrometer (μm), which equals one-millionth of a meter. The adoption of micro- as an official SI prefix occurred in 1960 during the 11th General Conference on Weights and Measures (CGPM), where it was standardized alongside other decimal prefixes to facilitate precise quantification in the metric system. Prior to its formal inclusion in SI, the prefix had been in use since the 19th century in various scientific contexts to denote minuteness, drawing from its Greek roots. In addition to its role in units of measurement, micro- functions as a combining form in English vocabulary to indicate small scale or microscopic phenomena, appearing in terms like —an instrument for viewing tiny objects—and , the study of microscopic organisms. This prefix plays a crucial role in disciplines ranging from physics and chemistry to biology and engineering, enabling concise notation for microscale phenomena and small-scale interactions. For instance, in electronics, it describes microfarads (μF) for capacitance, while in medicine, it quantifies micrograms (μg) for dosages. Its widespread application underscores the importance of standardized prefixes in promoting clarity and interoperability in global scientific communication.

Definition and Etymology

Core Meaning

The prefix "micro-" denotes a factor of one millionth, or 10−610^{-6}, in decimal-based measurement systems, particularly within the (SI). It derives from word mikros, meaning "small," and is used to scale SI base units quantitatively, such as forming the micrometer (μm) to represent one-millionth of a meter. Beyond its precise metric application, "micro-" also serves a qualitative role in language to signify something small or minute, independent of numerical scaling, as in "microfiction," which refers to very brief stories typically under 300 words. This usage appears in fields like and everyday terminology without implying the 10−610^{-6} factor. The formal standardization of "micro-" in the SI system ensures consistent scientific communication, distinguishing it from its broader descriptive applications. The prefix is commonly symbolized by letter mu (μ).

Historical Origin

The prefix "micro-" originates from the adjective mikrós (μικρός), meaning "small," "tiny," or "petty," which was Latinized as "micro-" and entered European in the to denote diminutive scales in emerging fields like and chemistry. This linguistic adoption reflected the growing interest in and minute phenomena, building on earlier 17th-century terms such as "," the Latin name for the newly invented . In the realm of standardized measurement, "micro-" gained formal status as a decimal prefix in 1874, when the British Association for the Advancement of Science (BAAS) introduced it within the centimeter-gram-second (CGS) system to express submultiples of units, specifically representing a factor of 10−610^{-6}. Pre-SI applications in the CGS framework included units like the microgram (μg), which measured one-millionth of a gram and became essential for precise chemical and physical analyses during the late 19th century. This marked a pivotal shift from ad hoc notations to systematic prefixes, facilitating international consistency in scientific reporting. The prefix's evolution culminated in its official incorporation into the International System of Units (SI) at the 11th General Conference on Weights and Measures (CGPM) in 1960, where it was explicitly defined as the multiplier for 10−610^{-6} to denote extremely small quantities across disciplines. This standardization built on the CGS legacy while extending the prefix's utility in the modern metric framework, ensuring its role in denoting scales like the micrometer for lengths or microfarad for capacitance.

Usage in Scientific Measurement

SI Prefix Designation

The micro- prefix is designated as one of the 24 SI prefixes used to form decimal submultiples of SI units, officially approved by the General Conference on Weights and Measures (CGPM) during its 11th conference in 1960 as part of establishing the International System of Units (SI). This prefix represents a multiplier of 10−610^{-6}, which is applied directly to the name or symbol of a base or derived SI unit; for example, one microsecond equals 10−610^{-6} seconds. In scientific writing and measurement, SI guidelines recommend the use of appropriate prefixes such as milli- (10−310^{-3}), micro- (10−610^{-6}), and nano- (10−910^{-9}) for expressing values to avoid cumbersome powers of ten and ensure numerical values remain on a convenient scale between 0.1 and 1000, while prohibiting the combination of prefixes, such as the invalid form micro-milli-. Prior to SI standardization, descriptive terms like "millionth" were commonly used to denote a factor of one millionth of a unit, but such alternatives have been deprecated in favor of the precise micro- prefix to promote uniformity and avoid ambiguity in technical contexts.

Symbol and Notation

The symbol for the micro- prefix in the (SI) is the Greek lowercase letter mu (μ), representing a factor of 10^{-6}. This symbol is uniquely derived from the Greek alphabet among SI prefixes, distinguishing it from the Latin-letter-based symbols for other prefixes. According to the SI Brochure, prefix symbols like μ are printed in upright (roman) , regardless of the surrounding text's style, to ensure clarity and consistency in . In notation, the μ is placed directly before without any intervening space or , forming a compound such as μm for micrometer or μg for . This rule applies universally to avoid and maintain compactness; for instance, a of one millionth of a meter is denoted as 1 μm, not 1 μ m. The NIST Guide to the SI emphasizes that prefix must be attached seamlessly to unit in this manner, with no spaces permitted between them. To prevent confusion with the milli- prefix symbol m (10^{-3}), the use of μ is mandatory in formal SI notation, as the two scales differ by three orders of magnitude. Historically, in informal or plain-text contexts lacking Greek character support, the Latin letter u has occasionally substituted for μ due to visual similarity and ASCII limitations, but this is not recommended and is restricted to legacy applications. The SI standards explicitly prohibit "u" as an official symbol to uphold precision, particularly in handwriting where μ might resemble m if not rendered carefully. Mathematically, the micro- prefix denotes a quantity as q=n×10−6×uq = n \times 10^{-6} \times u, where nn is the numerical value and uu is the base unit, with μ serving as the symbolic prefix in the unit expression (e.g., q=5×10−6 mq = 5 \times 10^{-6} \, \mathrm{m} or 5 μm5 \, \mu\mathrm{m}). This convention aligns with broader SI prefix rules for decimal submultiples, ensuring unambiguous representation in equations and measurements.

Encoding and Representation

Character Set Encoding

The micro symbol μ is encoded in Unicode primarily as U+03BC, the Greek small letter mu, which is the preferred code point for mathematical and scientific contexts, including SI unit prefixes. A separate compatibility character, U+00B5 (micro sign µ), exists for legacy support in applications that originated from 8-bit character sets, but it decomposes to U+03BC under Unicode normalization. This distinction arose with Unicode 3.2 in 2002, which established U+03BC as the recommended form for modern usage in SI notations to ensure consistent rendering and semantic accuracy across systems. Historically, the 7-bit ASCII standard lacks any encoding for the micro symbol, leading to common approximations such as the Latin letter "u" in representations of units like μm. Extended 8-bit encodings provided initial support; for instance, ISO/IEC 8859-1 (Latin-1) includes the micro sign at byte value 0xB5, facilitating its use in early Western European computing environments. In , the entity µ corresponds to U+00B5 for , while μ or μ renders U+03BC. In legacy systems, such as early PC environments using (OEM ), there was no native support for a precise micro symbol, resulting in substitutions like the graphical approximation at 0xE6 ( 230), which displayed a blocky variant rather than the intended glyph. This often caused display inconsistencies when migrating data to Unicode-compliant platforms, where the approximated character might map incorrectly or require manual replacement with U+03BC.

Typographic Variations

The typographic rendering of the micro symbol μ adheres to established guidelines for clarity in . The (SI) specifies that prefix symbols like μ, when used in units (e.g., μm for micrometer), must be printed in upright (roman) typeface rather than italic, to differentiate them from symbols representing physical quantities. In technical documents, fonts are often used for such symbols to improve legibility, especially in diagrams and on screens where fine details must remain distinguishable. Variations in the design of μ occur across font families, particularly in typefaces, where the tail often curves differently—ranging from a subtle hook to a more elaborate loop—which can occasionally lead to visual confusion with the Latin letters "u" or "v" in suboptimal designs. In East Asian , μ is commonly rendered narrower to align with the compact proportions of CJK scripts, facilitating better integration in mixed-language layouts. Low-resolution displays pose rendering challenges, where the symbol's tail may not resolve clearly, resulting in misreading as "m" and emphasizing the need for vector-based or high-DPI formats in digital publications. For precise typesetting, the LaTeX command \mu produces μ in math mode, and the siunitx package ensures upright rendering with appropriate for unit combinations, such as \micro\meter yielding μm.

Applications Across Fields

In Physics and Engineering

In physics, the prefix "micro-" quantifies subtle and field intensities, such as in microwatts (μW), which measures flux at levels as low as 1 μW in photonic devices and optic systems. For example, specialized calorimeters detect microwatt-level to establish transfer standards in precision metrology. Similarly, magnetic flux is expressed in microteslas (μT), where 1 μT equals 10^{-6} tesla, facilitating measurements of weak fields like the Earth's geomagnetic field, typically 25–65 μT at the surface. In , "micro-" denotes component scales critical to functionality, as in the microfarad (μF) for in electronic circuits, where 1 μF = 10^{-6} farads enables in filters, timing circuits, and power supplies. In precision , the micrometer (μm) unit, equivalent to 10^{-6} meters, supports tolerances below 1 μm for manufacturing high-accuracy parts like and shafts. This prefix bridges microscale to nanoscale measurements, exemplified by visible light wavelengths spanning ~0.4–0.7 μm, which informs and processes. In semiconductor engineering, feature sizes evolved from several micrometers in the 1970s (e.g., 6 μm nodes in ) to sub-micrometer scales by the , transitioning to nanometers thereafter to drive density increases.

In Biology and Medicine

In , the prefix "micro-" is applied to describe entities and scales at the microscopic level, most notably in the study of microorganisms. , a primary class of microorganisms, typically range in size from 0.5 to 5.0 micrometers in length, allowing them to be observed only under and highlighting the prefix's role in denoting this subvisible domain. The concept of microorganisms was introduced through Antonie van Leeuwenhoek's observations in the 1670s using self-crafted microscopes, where he first described these "animalcules" in samples like and pond water, laying the groundwork for despite not employing the term itself. This approach was formalized in the with the adoption of "microorganism" around 1880, coinciding with taxonomic advancements by figures like and that classified these entities within biological systems. Biochemical processes further utilize "micro-" for concentration measurements, such as micromolar (μM), which denotes 10^{-6} moles per liter and is standard for expressing substrate levels in . For instance, the Michaelis constant (K_m), representing the substrate concentration at half-maximal reaction velocity, is frequently reported in μM for many enzymes, providing insight into binding affinities and reaction efficiencies without requiring exhaustive listings of specific values. In , "micro-" facilitates precise dosing and diagnostic scales aligned with physiological minima. Drug dosages are often specified in micrograms (μg), as seen in medications like insulin or certain antibiotics, where therapeutic amounts are critically small to avoid while achieving . Similarly, blood tests employ microliters (μL) for sample volumes, with complete blood counts reporting cell densities per μL—such as at 4,000 to 11,000 per μL in healthy adults—to detect abnormalities efficiently from minimal draws. A key clinical application involves assessments, where human immunodeficiency levels are quantified in RNA copies per milliliter of plasma, with thresholds below the limit of detection, generally less than 20 copies/mL, indicating successful suppression and guiding antiretroviral therapy decisions.

Abbreviating Practices

In formal writing and prose, the prefix "micro-" is generally spelled out in full to maintain clarity and avoid , particularly in non-technical contexts where readers may not be familiar with symbols. This practice ensures precise communication without relying on specialized notation. In technical documents, tables, and data presentations, the prefix is often abbreviated using the Greek letter mu as "μ-", prefixed to the unit symbol, as detailed in the section on symbol and notation. A common in and medical contexts is "mcg" for microgram, adopted specifically to prevent handwriting errors where the symbol "μg" might be misread as "mg" (milligram), potentially leading to a thousandfold dosing overdose. The U.S. (FDA) recommends "mcg" over "μg" in labeling and documentation to mitigate such risks, emphasizing its use in printed materials like prescriptions and product inserts. For nutrition labels on and dietary supplements, the FDA's guidelines specify "mcg" as the primary for micrograms, with "μg" permitted as an alternative, establishing this convention to promote safety and standardization in consumer-facing information. In informal engineering notes and quick sketches, particularly in fields like and where the micro symbol may be unavailable on keyboards or in handwriting, "u" is occasionally used as a substitute for "micro-," resulting in notations like "uf" for microfarad. However, this is not recommended for formal publications due to potential confusion with other units. Abbreviations such as "M" are strictly avoided for "micro-" because it conflicts with "mega-" (10^6) in scientific measurements and "M" for in chemistry, which could lead to significant interpretive errors. In legal metrology, which governs the accuracy of measuring devices used in , abbreviations for prefixes like "micro-" must be unambiguous and not alter the intended meaning or performance of the device, ensuring reliability in trade and enforcement. This requirement is outlined in the NIST Handbook 44, which provides specifications for tolerances and technical requirements to prevent misinterpretation in official markings and calibrations.

Comparison with Other Prefixes

The micro- prefix, denoting a factor of 10^{-6}, represents a scale three orders of magnitude finer than the milli- prefix (10^{-3}), enabling precise measurements in applications requiring higher resolution, such as where timing circuits distinguish between milliseconds (ms) for broader event durations and microseconds (μs) for rapid , as seen in power system synchronization where phase angle accuracy demands microsecond-level precision. In contrast to the nano- prefix (10^{-9}), micro- applies to microscale phenomena on the order of micrometers, such as the size of biological cells (typically 1–100 μm), while nano- addresses nanoscale structures like DNA strands (about 2 nm wide), with technological focus shifting toward nano- applications in the early 2000s amid growing commercial adoption of nanomaterials. Although all SI prefixes maintain coherence in forming decimal multiples and submultiples of base units, micro- stands out by employing the Greek letter μ as its —derived from "mikros" meaning small—unlike the Latin-derived symbols for adjacent prefixes like milli- (m) and nano- (n). A practical distinction arises in contexts, where the (MB, using the mega- prefix for 10^6 bytes in ) and (μs) coexist without symbol conflict due to their separation into storage capacity and time measurement domains, respectively, adhering to SI conventions for the latter while storage often incorporates binary interpretations.

References

  1. https://www.nist.gov/pml/owm/metric-si-prefixes
  2. https://www.etymonline.com/word/micro-
  3. https://schemas.optimade.org/releases/v1.2.0/v1.2/prefixes/si/micro
  4. https://membean.com/roots/micro-small
  5. https://usma.org/si-prefixes-and-their-etymologies
  6. https://www.bipm.org/en/measurement-units/si-prefixes
  7. https://www.merriam-webster.com/dictionary/micro-
  8. https://www.iec.ch/history-si
  9. https://www.bipm.org/en/committees/cg/cgpm/11-1960/resolution-12
  10. https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf
  11. https://www.nist.gov/pml/owm/writing-si-metric-system-units
  12. https://www.unicode.org/reports/tr25/tr25-16.html
  13. https://www.fileformat.info/info/charset/ISO-8859-1/list.htm
  14. https://www.toptal.com/designers/htmlarrows/punctuation/micro-sign/
  15. https://www.ascii-code.com/CP437
  16. https://learn.microsoft.com/en-us/windows/win32/intl/code-page-identifiers
  17. https://iupac.org/wp-content/uploads/2016/01/ICTNS-On-the-use-of-italic-and-roman-fonts-for-symbols-in-scientific-text.pdf
  18. https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-10-more-printing-and-using-symbols-and-numbers
  19. https://forums.autodesk.com/t5/autocad-forum/mu-micron-symbol-displaying-as-m-autocad-lt-2009/td-p/5956284
  20. http://ieeexplore.ieee.org/document/126629/
  21. https://www.thefoa.org/tech/ref/testing/test/power.html
  22. https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/measuring-magnetic-fields
  23. https://www.electronics-tutorials.ws/capacitor/cap_1.html
  24. https://mrmmetrology.com/blog/micrometers-precision-measurement-guide-2025/
  25. https://www.osti.gov/servlets/purl/1646153
  26. https://microbenotes.com/bacterial-sizes-shapes-arrangement/
  27. https://royalsocietypublishing.org/doi/10.1098/rsnr.2004.0055
  28. https://www.merriam-webster.com/dictionary/microorganism
  29. https://www.ncbi.nlm.nih.gov/books/NBK604207/
  30. https://clinicalinfo.hiv.gov/en/guidelines/hiv-clinical-guidelines-adult-and-adolescent-arv/plasma-hiv-1-rna-cd4-monitoring
  31. https://selinc.com/api/download/111663/
  32. https://nanohub.org/resources/26670/download/Comparison_of_scale_Presentation.pdf
  33. https://nanosense.sri.com/activities/sizematters/sizeandscale/SM_Lesson2Student.pdf
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC6982820/
  35. https://physics.nist.gov/cuu/Units/binary.html
Add your contribution
Related Hubs
Contribute something
User Avatar
No comments yet.