An algebraic expression does not always need a constant and coefficient. An expression is a combination of numbers, variables, and operations, and it can consist of any combination of these elements. For example, an expression could be as simple as a single variable (such as "x"), or it could be a more complex combination of terms (such as "3x^2 - 5y + 2").
Algebraic expressions always have variables, coefficients, and mathematical operations (such as addition, subtraction, multiplication, and division). The expressions may also contain constants (such as 2, 3, or -7), exponents (such as x^2 or y^3), and/or mathematical symbols (such as parentheses or square roots). The form and complexity of the expression can vary widely depending on the specific problem or context.