Other forms: corroborations
If you tell your boss you couldn't go to work because you were sick and then produce a doctor's note, that's corroboration — a fancy term for "evidence" — something that backs up a statement or a theory.
Corroboration is probably the kind of word you wouldn't use in casual conversation; you would more likely use proof, for example. It's generally used in a more technical or formal sense, regarding a legal case, perhaps, or a scientific experiment, as in: "Physicists today are finding increasing corroboration that Einstein's theories were correct."