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How do constants differ from variables in algebra?

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Map of the Greco-Roman world highlighting the birthplaces of notable ancient mathematicians, marked with the pi symbol and labeled with their names. Cities such as Athens, Alexandria, Syracuse, and Miletus are shown around the Mediterranean, with modern country boundaries outlined. An inset provides detail for the region of Greece and western Anatolia. — algebra This map spans a millennium of prominent Greco-Roman mathematicians, from Thales of Miletus (c. 600 bce) to Hypatia of Alexandria (c. 400 ce).

In algebra, the primary difference between a constant and a variable lies in whether the value remains fixed or can change within a given context.

Variables: A variable is a symbol, typically a letter such as x, y, or t, that represents an unknown numerical value or a quantity that can change. In an algebraic equation, variables are the components for which you solve to satisfy the equality.12
Constants: A constant is a value or object that maintains a fixed magnitude throughout a specific operation or discussion. While some constants are absolute—meaning they have the same value wherever they occur, such as pi ( $π$ )—others may be defined as a variable that is restricted to assuming only one specific value in a given context.34

In equations like the quadratic form $a x^{2} + b x + c = 0$ , the letters a, b, and c often represent coefficients (fixed values that must be specified), while x serves as the variable.1