Here and throughout the course, what we mean by linguistic evidence is the linguistic data that form the basis for your conclusion - in other words, expressions together with associated grammaticality judgments.

For instance, is the underlined noun phrase in (1a) a complement or an adjunct of the italicized verb? (1b) is evidence that it is an adjunct.

(1) a.   They partied the entire weekend.
b. They did so the entire weekend.

What about the status of the same string in (2a)? In this case, (2b) is evidence that the expression is a complement rather than an adjunct.

(2) a.   They enjoyed the entire weekend.
b. * They did so the entire weekend.

Even though (1b) and (2b) differ in grammaticality, their status as evidence (that is, as the basis for drawing conclusions) is the same.