What is Evidence?

In a series of meetings related to epistemic concepts, this week let us talk about another important scientific concept to which many make appeals, but how many well understand it?

What is the nature of "evidence"? Often these days one hears talk of "reason" and "science" as holding "degrees of belief in accord with the available evidence" etc. Just what do they mean?

How does the institution of "science" use this concept?

My current favorite is as follows, we can use this as a jumping off point, if you have another please bring it up!

Evidence: A piece of information/data whose presence or absence effects the likelihood of a hypothesis.

With this definition we see a "relativist" conception, that evidence is evidence only in relation to a particular hypothesis. Any data point may or may not be evidence at any time, given some community's treatment of it as relevant to a hypothesis. What do you all think?