(noun)

1. A short note acknowledging a source of information or quoting a passage
2. An indicator that orients you generally
3. A book to which you can refer for authoritative facts
4. The class of objects that an expression refers to
5. The act of referring
6. A publication (or a passage from a publication) that is referred to
7. The relation between a word or phrase and the object or idea it refers to

Check out the below links to see where we find our sources of reference.