Are a pure substance and a substance the same thing?

Question

Really, the simplest questions have the most complicated - and vaguest - answers.

Answer 1

Theoretically yes, since an impure substance is a mixture or compound. So, if we simply say water, we mean pure water or water with impurities insignificant or below some detectable limits.

Answer 2

It depends on the context you are using the word "pure". Chemistry is a wonderful science and in chemistry terminology, purity means the absence of any other elements.