How to type Omega

Ω lives in the Greek and Coptic block (U+0370-U+03FF), the Greek alphabet, used throughout mathematics and the sciences. Within Unicode it is classified as Lu, an uppercase letter. It has a lowercase counterpart and changes under case conversion. Its bidirectional class makes it left-to-right.

Its lowercase counterpart is ω (U+03C9). They are separate codepoints, so a byte comparison treats them as different characters even though a case-insensitive search does not.

How to type Ω in Microsoft Word and on Windows

In Microsoft Word, type 03a9 and press Alt + X. Word reads the four characters before the cursor as a hex codepoint and replaces them, and pressing Alt + X again turns Ω back into 03a9, which is the quickest way to check what a character really is.

On Windows, hold Alt and type 234 on the numeric keypad.

On a phone, neither iOS nor Android has a codepoint route. Copy Ω from this page once, then add it as a text replacement (Settings, General, Keyboard on iOS) so a short abbreviation expands to it from then on.

What Omega is used for

In mathematical notation Ω is a variable: it stands for a quantity rather than acting on one, so an equation treats it the way it treats x, and the spacing around it is the spacing around a letter. That is the classification unicode-math gives it, and it is what decides how the symbol is set: $\mupOmega$ in LaTeX, in maths mode rather than in a sentence.

The command is \mupOmega rather than the \Omega most people reach for, and the difference is not cosmetic: mup is unicode-math for maths, upright, and this codepoint is the upright letter. Plain LaTeX's short command gives the sloped math-italic letter, which is a different character with a different codepoint. Copying Ω into an equation gets you the upright one.

Ω is a letter before it is a symbol, and on the Greek keyboard layout it is simply Shift and V: the key your keycap already calls V. That is the route when you are typing Greek rather than reaching for one character. How to type Greek on a keyboard has the whole map.

What Ω gets confused with

Ω has lookalikes that are a different character underneath. Search, sorting and anything that compares strings can tell them apart even where a reader cannot.

ω (U+03C9) is small omega, the lower case of this letter.

0 (U+0030) is the digit zero, which is what an omega becomes when the font has no Greek coverage and the text falls back.

What Unicode says about Omega

The code chart points from Ω to ohm sign (U+2126) and inverted ohm sign (U+2127). These are the characters the standard thinks you might have meant instead, which makes them the ones worth checking when Omega looks nearly right but not quite.

How Omega behaves in software

Ω is East Asian Ambiguous: one column in a Western locale and two in a CJK one. That is why a table that lines up on your machine can break on somebody else's, with no change to the text at all. It is a left-to-right character, so it holds that direction even inside a right-to-left paragraph.

What people ask about Omega

Every way to write Omega

Encodings and escapes for Omega (Ω)

Form	Value
Codepoint	U+03A9
Decimal	937
UTF-8 bytes	CE A9
UTF-16 bytes	03 A9
HTML entity	Ω
HTML numeric	Ω or Ω
CSS	\03A9
JavaScript	\u03A9
Python	\u03A9
URL-encoded	%CE%A9
LaTeX, in maths mode	$\mupOmega$
SVG	03A9.svg · PNG (SIL Open Font License)

If Ω arrives as Ω

That is this exact character, undamaged: its two UTF-8 bytes CE A9 are being read one at a time as Windows-1252. The Latin-1 range is where this happens most, because it is the range every legacy system thought it already handled. Nothing is lost, and retyping will not help: the fix is at the reading end, which has to be told the text is UTF-8. An empty rectangle is the opposite complaint, and means the encoding is right and the font has no glyph for U+03A9.