Is It a Mode Shape, or an Operating Deflection Shape?
Mode shapes and operating "deflection" shapes are related to one another. In fact, one is always measured in order to obtain the other. Yet, they are quite different from one another in a number of ways.
Please explain and summarize the difference in a page.

Ref) Mark H. Richardson, "Is It a Mode Shape, or an Operating Deflection Shape?", Sound & Vibration Magazine 30th Anniversary Issue March, 1997.