Not sure what a P/E Ratio is? Or how it differs from a P/B or P/S?
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To access Hoovers' Glossary select the Help link on the right half of the Home Page, then FAQs / Glossary, then Glossary.
Credo Reference contains several business related dictionaries and encyclopedias. Hint: First search for your term, then limit your results to "Business" in the All Subject Dropdown Box.
Here is a list of links to dozens of specialized online business glossaries: