Example:
Requiremnet:After successful login homepage should be logged in.
Funtional Testing test case:
Verify that when correct username and password is entered homepage is displayed.
Expected Result : Home page should be displayed.
Actual Result: Error message is prompted "Page cannot be displayed".
Usability Defect : When a user does not find a software product understandable, easy to learn, easy to operate and attractive.

Example:
Usability Testing test case:
Verify that homepage should have a content in Japanese Language.
Expected Result : Home page have a content in Japanese Language.
Actual Result: Home page have a content in English Language