What is the difference between a rational expression and a polynomial?

A rational expression is specifically defined as a fraction where both the numerator and the denominator are polynomials. This means that it can take the form of one polynomial divided by another, which can also include cases where the denominator is not zero. For example, ( \frac{x^2 + 3x + 2}{x - 1} ) is a rational expression because both the numerator ( x^2 + 3x + 2 ) and the denominator ( x - 1 ) are polynomials.

In contrast, a polynomial itself is a mathematical expression that consists of variables raised to non-negative integer powers and summed together, such as ( x^3 + 2x^2 - x + 5 ). Polynomials do not include division by another polynomial, which is key to distinguishing them from rational expressions.

Thus, the correct answer highlights the fundamental relationship between rational expressions and polynomials, emphasizing that rational expressions involve the division of polynomials, distinguishing them from standalone polynomial forms.