Use case: Is nothing but how to use the Application or 
project...

Based on Usecase understand we will write test case...

Test case: Hoe to test the application or project... in 
test case we will specify all prerequisite(settings to 
execute) and Test data and what u r expecting from that 
usecase.

Test case: Test case is nonthing but its a document to use 
and found bugs in that applciation. give many possible 
inputs and expect from the expected result if any deviation 
found in the expected result means it has a bug

Firstly, Test case is the details description of what to be 
tested, what data to be given and what actions to be taken 
to check the actual result against the expected result.
 
Now, simply Use Case is the pictorial defination of 
Requirements. So, looking at the use cases, you can write 
the test sceanarios and then eventually details step by 
step ..Test cases.

An Use Case which describes how a Service / System will be 
defined to the end user . Use Case includes who are the 
Actors / Roles involved in the functionality.

Based on the Use Cases we will prepare Test Cases ...Test 
Case which describes how the System works accroding to the 
functionality [Step by Step ...]

With out preparing Use Case also we can prepare Test Cases 
based on SRS.

Test case is a document prepaired by test enginner and it
can be defined as a set of applicable test that need to be
conducted on system to validate or not..

plz correct me if i am wrong...