The letter "ι" is the ninth letter of the Greek alphabet. It is pronounced like the English letter "i" in words such as "machine" or "ski." In the Greek numeral system, "ι" represents the number 10. In modern Greek, "ι" can appear in both uppercase (Ι) and lowercase (ι) forms. It is commonly used in various Greek words and is an essential part of the language's phonetic structure. The letter is also found in related topics such as Greek language and Greek culture.