Find Definitions

Looking for a quick definition?

We’ve got loads of key subject terms in our subject glossaries. There are three ways of finding what you are looking for:

  • First click on the letters of the alphabet to browse for terms.
  • Select a subject from the drop-down menu above to filter the terms by Subject.
  • Or lastly, type the term you are looking for into the search box.


Here are some examples of the kinds of definitions you’ll find on this page.

Select a subject
Search for a definition...

the seepage of acidic, contaminated water from disused mines and mine dumps.


rain that contains high levels of sulfuric acid, hydrochloric acid and nitric acid.


animals that lack a cavity between the digestive tract and the outer body wall.


a disease caused by the human immunodeficiency virus (HIV).


the immunity an organism develops during its lifetime.