The horseshoe-shaped capital letter used to denote the ohm, the SI unit of electrical resistance — visually identical to, but formally distinct from, the Greek letter omega.
Also known as: U+2126 OHM SIGN
Sometimes confused with: Omega
A dedicated Unicode code point (U+2126 OHM SIGN) exists for the electrical-resistance symbol, but the Unicode Standard's own documentation recommends using the Greek letter omega (U+03A9) instead, and normalisation silently collapses the two — a real, documented encoding-confusability issue, not a cultural symbol with contested meaning.
Denotes the ohm, the SI unit of electrical resistance, named after physicist Georg Simon Ohm. The unit was standardised by a British Association committee (1861–1867), formally recommended as the 'international ohm' in 1893, and fixed within SI at the 9th–11th General Conferences on Weights and Measures (1946–1960).
1861–1960
The Unicode Standard maintains U+2126 OHM SIGN as a distinct code point purely for backward compatibility with legacy character sets, but its own Names_List_Comment states the 'preferred representation is 03A9' (the Greek letter omega) — U+2126 has a canonical decomposition to omega and is silently collapsed into it by standard Unicode normalisation (NFC/NFD/NFKC/NFKD). In practice, most keyboards, OCR and copy-paste operations produce plain omega, not the dedicated ohm sign.
This is a technical encoding fact, not a claim about the underlying Greek letter itself — Unicode's own character properties classify U+2126 as effectively a Greek-script letter, not an independent symbol.
A horseshoe-shaped capital letter, open at the bottom, typically with serifs — visually indistinguishable from the Greek letter omega in almost all typefaces.
This sign is the capital Greek letter omega, encoded separately in Unicode for compatibility. Whether a capital omega means resistance or the letter depends entirely on where it appears.