You use encyclopedia for when you are researching something or someone.
You use an encyclopedia for looking up information and recourse's.
I use an encyclopedia to do my homework.
An encyclopedia is usually found in a library
That subject was deleted from this year's encyclopedia. Unfamiliar with Namibia, Bill had to look up its entry in the encyclopedia.
wiki answers, or an atlas, or an encyclopedia.
Advantages of the printed encyclopedia include that they are still a reliable source for information. You are able to use a printed encyclopedia for research even if you do not have internet access.
To find out various things about the world x