Constant - A fixed value. In Algebra, constant is a number on its own, or sometimes a letter such a t, u and v to stand for a fixed number.
Coefficient - A number used to multiply a variable. Eg, tx means t times x, and "x" is the variable, "t" is the coefficient.
Variable - A symbol for a number we don't know yet. It is usually letter x or y. Eg, y + 2 = 8, y is the variable.
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