In general, reliability in research refers to consistency in a study or measurement test; validity refers to accuracy.
However, these concepts are much more complex in actual research practice than these broad definitions (validity in particular). The following are very useful resources for more information.
Look at the SAGE Research Methods tool in our library. Do individual searches on validity and reliability. The results include a range of definitions and explanations in encyclopedia, dictionaries, and handbooks.
An open web text for social science research, Research Methods Knowledge Base, is another solid resource for information on these two important research concepts. Scroll down for the sections on validity and reliability.
