By Maya Chen, lettering designer and type educator · Checked by Jordan Hale · · How we review content
Key facts
- Ω is the SI symbol for the ohm and μ is the SI prefix symbol for micro (one millionth), both fixed by the SI Brochure.
- The ISO 80000 series lists λ for wavelength, ω for angular frequency and ρ for density as preferred quantity symbols, while allowing alternatives.
- Most Greek-letter meanings are conventions: sigma is a standard deviation in statistics, stress in engineering and conductivity in physics.
- Iota, omicron and upsilon are rarely used as variables; omicron looks like Latin o and is avoided for that reason.
- The summation sign ∑ (U+2211) and product sign ∏ (U+220F) are separate characters from the letters Σ (U+03A3) and Π (U+03A0).
What do Greek letters in math and science mean?
Every Greek letter below lists the meanings you are most likely to meet, grouped by field. They are conventions: a physics paper may reuse σ for something that is not on this list, and a textbook may swap α and β. Treat the entries as a map of what to expect, not as a rulebook.
Which meanings are fixed by a standard?
Where a standard fixes a symbol, the note says so. These are the Greek-letter symbols that are standardised in a firm way:
- Ω is the SI symbol for the ohm, the unit of electrical resistance (SI Brochure).
- μ is the SI prefix symbol for micro, one millionth (SI Brochure). The brochure also lists the other prefixes, which are Latin letters.
- Quantity symbols such as λ for wavelength, ω for angular frequency or ρ for density are the preferred symbols in the ISO 80000 series, with the clarification that a quantity may have alternative symbols.
Which meanings are only convention?
Everything else here follows common textbook practice. If you are writing for a journal, course or company, follow its style guide over this page.
Which Greek letters are rarely used as symbols?
Iota, omicron and upsilon are rarely used as variables. Omicron looks like Latin o and is avoided for that reason, and the big-O and little-o notation of computer science uses the Latin letter. Upsilon appears in particle physics, for example in the upsilon meson. Do not expect them in everyday formulas.
Which Greek characters should I copy with care?
Several maths symbols have a Greek twin that is a different character. The summation sign ∑ (N-ARY SUMMATION, U+2211) is not the letter Σ (U+03A3), and the product sign ∏ (U+220F) is not Π (U+03A0). If a document needs to be searchable, or if the text will pass through software that cares, use the right one. The Unicode page has the full list.
Where can I copy or type these letters?
The copy and paste Greek alphabet page has the plain letters. For ways to type them, see how to type Greek letters. Maths signs and units with copy buttons are at math symbols and science symbols. Sigma, delta, pi, omega and mu have their own pages that go deeper on uses, codes and lookalikes: sigma, delta, pi, omega and mu.
How do I write these letters in LaTeX?
Each letter has a LaTeX command in math mode, and a few capitals have none. The full command list, variant forms such as \varepsilon, bold and upright Greek are on LaTeX Greek letters.
Sources
The standardised items above come from the SI Brochure and the ISO 80000 series. The by-field entries for Greek letters in math and science are conventions assembled from standard textbook usage and cross-checked against the secondary overview listed below. We have not verified each entry against a primary standard, and conventions differ by country, field and publisher.
- ISO 80000-2:2019, Quantities and units: Mathematics
- BIPM, The International System of Units (SI Brochure)
- NIST Special Publication 811, Guide for the Use of the International System of Units
- NIST CODATA fundamental physical constants (fine-structure constant, Stefan-Boltzmann constant)
- IUPAC Green Book, Quantities, Units and Symbols in Physical Chemistry
- Wikipedia, Greek letters used in mathematics, science, and engineering (secondary overview)
Frequently asked questions
Basics
Why do scientists use Greek letters in math and science?
Is the meaning of Greek letters in math fixed?
Why does pi have so many uses?
Which Greek letters have meanings fixed by the SI?
Which Greek letters are rarely used as variables?
Where it works
What is the difference between Δ and ∆?
Which Greek letter is used for the micro prefix?
Is there a standard for Greek letters in math and science?
How it works
Are λ, ω and ρ official symbols?
Where can I check the official meaning of a symbol?
Tips & limits
Is the summation sign ∑ the same as Σ?
Which should I follow, this page or my style guide?
Related
- Greek AlphabetThe Greek alphabet has 24 letters, from alpha to omega, each with an uppercase and a lowercase form. Tap any letter to copy it, check its name, sound and numeric value in the table, or print a clean one-page chart. This page treats the letters as characters and symbols, not as a language course.
- Greek Alphabet UnicodeThe Greek alphabet Unicode block, Greek and Coptic (U+0370 to U+03FF), holds all 24 letters: capitals at U+0391 to U+03A9 and lowercase at U+03B1 to U+03C9. This page lists each code point, HTML entity and LaTeX command, plus the micro sign, ohm sign and homoglyph traps.
- How to Type Greek LettersHow to type Greek letters on any device: add a Greek keyboard on Windows, Mac, iPhone or Android, or use Alt+X in Word and UNICHAR in Excel for a single character. Copying from the alphabet page works everywhere. Each method notes what we verified and which traps to avoid.
- Text Symbols to Copy and PasteText symbols are Unicode characters, such as hearts, stars, arrows, check marks and brackets, that you copy and paste into bios, names, messages and documents. Each one shows its Unicode name and code point, so you know exactly what you are pasting and can tell it apart from an emoji.
- Fancy Letters A to ZEvery letter of the alphabet in every Unicode style, with code points.
- Lettering Image MakerThis lettering generator draws your words in 16 display fonts, from bubble and graffiti to Old English and neon. Pick colours and effects, then download a sharp PNG.