Can anyone explain why the Fundamental Theorem of Algebra and the Fundamental Theorem of Calculus are called "Fundamental"? The algebra theorem states that every non-constant single-variable polynomial with complex coefficients has at least one complex root. The calculus theorem states that an indefinite integration can be reversed by a differentiation and that a definite integral of a function can be computed by using any one of its infinitely many anti-derivatives. According to Wikipedia, the Fundamental Theorem of Algebra is not fundamental for modern algebra; its name was given at a time in which algebra was basically about solving polynomial equations with real or complex coefficients. In any case, what's is fundamental about these theorems? This is a word useage question more than a math question.