last test case which wre failed last time test again is 
called re testing..some extra enhancement,or modification 
on ur module then regression testing...

Retesting : testing the application with the same input 
data again & again.

Regression Testing: is done after some changes has been 
made or some new features has been introduce in the 
application to determine whether the changed components has 
introduced any error in unchanged components

Correct me if I m wrong

Regression testing is nothing but any modification is done 
with out affecting the already existing previews.

Retesting is done when a bug is rectified after the initial 
testing.

REGRESSION TESTING IS done on the same bulild again and 
again.
RETESTING MEANS testing the build with multiple sets of data

Re testing:- Testing an application again & again for same
input.


Regression test:-  Regression test is conducting after smoke
test. The reason for conducting regression test is to check
for side effects OR impact on build due to code changes.
[bugs are fixed by making code changes]

Retesting means testing on the same build with different 
inputs.

Regression testing involves testing after the bug is being 
fixed by the developer to check whether it has affected 
other modules of the build.

correct me if i am wrong.

Retesting:Testing an application with set of data

Regression testing : Testing an application after some 
changes has been made to the application.Changes can be 
done in two scenarios as mentioned below

1)When new changes has incorporated in to the application

2)When defects found.Development Department will correct 
those defects

If there are 20 Test cases in a module, in the first cycle 
the test cases 8,9,10 has been failed, once the issues has 
been fixed and testing only testcase 8,9,10 is called Re-
Testing. 
Testing the build with all the 20 testcases is called 
Regression Tesing

Regression Testing:

It is the testing to ensure that the newly added 
functionality does not affect the existing functionality.

Re Testing:

Once the defect has been raised is fixed by the developers 
Re testing is done to ensure that the functionality works 
as expected and to close the defect

Retesting--- revaliding the bug fix
regresion testing is th eprocess of verifying that the s/w
changes have not broken the existing functionalities

retesting:
          the resting means the project is testing again and
again.
regression testing:
                 the regression testing is if have any
modifies and  quires that should be tested again

retestint means the project is tesing again and again.... 
and regression testing is if have any change in future then 
if we change the one module then we chack the others module 
also.... because we change the one module then this can do  
any effects in others module...or this is very complex work 
so we used this automation tool