Greek letters are characters from the Greek alphabet, which has been used since the 8th century BCE. The alphabet consists of 24 letters, including both uppercase and lowercase forms. Greek letters are commonly used in various fields such as mathematics, science, and engineering to represent variables, constants, and specific concepts. For example, the letter π (pi) represents the ratio of a circle's circumference to its diameter. In addition to their mathematical significance, Greek letters also hold cultural importance. They are often used in fraternities and sororities to signify membership and identity. Each letter can symbolize different values or principles, making them an integral part of social organizations and academic traditions.