Omega Symbol (Ω, ω): Meaning, How to Type It, and LaTeX

The omega symbol is Ω in uppercase and ω in lowercase — the twenty-fourth and final letter of the Greek alphabet. Uppercase Ω is the unit of electrical resistance, the ohm. Lowercase ω usually means angular velocity or angular frequency. Copy either below, or jump to how to type it on any keyboard.

Copy and paste: click either card above to copy the character straight to your clipboard — Ω for the ohm and for uppercase use, ω for angular frequency. Both paste cleanly into Word, Google Docs, Slack and any modern editor.

What the omega symbol means

Omega is the last letter of the Greek alphabet, which is why “alpha and omega” means the beginning and the end. In technical writing the two cases mean entirely different things, and mixing them up changes the meaning of an equation.

Ω as the ohm: resistance

One ohm is the resistance that lets one ampere flow under one volt. Ohm’s law is where most people first meet the symbol:

Resistance in series adds directly; in parallel the reciprocals add:

ω as angular frequency

Lowercase omega counts radians per second rather than cycles per second, so it carries a factor of 2π compared with frequency f:

It links rotational and linear motion, and it drives the reactance terms in AC circuit analysis — which is how both omegas end up in the same equation:

How to type the omega symbol

Windows

• Uppercase Ω: hold Alt and type 234 on the numeric keypad
• Lowercase ω has no legacy alt code. Press Windows + . to open the emoji and symbol panel, then search “omega”
• In Microsoft Word, type 03C9 and press Alt + X to convert it in place

Mac

• Uppercase Ω: Option + Z
• For ω, open Character Viewer with Control + Command + Space and search “omega”
• Or enable the Greek keyboard in System Settings → Keyboard, where ω sits on the v key

HTML and the web

• Ω or Ω for Ω
• ω or ω for ω

The omega symbol in LaTeX

Both cases are single commands, and both belong in math mode. Uppercase Greek is upright by default; add \varOmega (with the amsmath package) if you want it italic to match the lowercase letters:

For the unit rather than the letter, use siunitx so the spacing and upright shape follow the SI rules:

Frequently asked questions

What is the difference between Ω and ω?

Case. Uppercase Ω is the ohm, a solid angle, or a sample space. Lowercase ω is angular frequency or the first infinite ordinal. They are not interchangeable.

Is the omega sign the same as the ohm sign?

In practice, yes — the ohm is written with the Greek capital omega. Unicode has a distinct OHM SIGN at U+2126, but it is deprecated in favour of U+03A9.

What does ω mean in physics?

Angular velocity or angular frequency, measured in radians per second. For circular motion it relates to linear speed by v = ωr, and to ordinary frequency by ω = 2πf.

For the rest of the alphabet, see our guide to Greek letters and symbols in LaTeX, or the sigma symbol and alpha symbol.

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