1. the 15th letter of the Greek alphabet (Ο, ο)

Examples

• The Greek letter omicron looks similar to the English letter O.
• In mathematics, omicron is sometimes used as a variable symbol.
• Students learning Greek must memorize the order of letters including omicron.
• The word omicron comes from Greek meaning ‘small o’.
• Omicron appears between xi and pi in the Greek alphabet.