1.What is the Difference between Use Case and Business Requirement?
2.What is the Difference between Business Requirement and Business
3.What is the Difference between Use Case and Business Rule?
Re: Diff between Use case and Business Requirement
If your asking questions like these I suggest you read up on UML design, if you don't understand these terms mere definitions are not going to help you. After this you need to do as lynneM suggested and put the usage of the terms into context of where you work and how they use (and often mis-use) such terms.