conducting testing on the same build, is called retesting 
and 
conducting testing on the modified build is called 
regression testing.

a)	Retesting is nothing but same application with 
execution the multiple test data.
b)	It is so many phase doing in test life cycle
c)	Regression testing is nothing but re execution of 
the modified build is called the regression testing
d)	That when all bug are solved then time do this test
e)	Then that time developer or client had some changes 
that changes based test is called the regression test


My name is k.chandra sekhar,
My phone no are 9246540049 65880049 ,Hyderabad.
My mail id is ndra_143@yahoo.co.in 
I am take the class for projects if you interst contact
If any body want full explain send the mail

Retest:Reexicution of testcases on the same build,Ex:
DDT(Data driven testing)
Regresssion testing:reexicution of the testcases on the 
modified build.

Retesting - Testing of the same features everytimne 
focusing on the functionality verification.

Regression- Testing the features for fucntionality & also 
focusing on possible side effects during testing.

regression testing : the re-execution of all test cases on 
a modified build to ensure bug fix works and occurence of 
any side effictives.

re-testing: the re-execution of affected test case on a 
modified build

Retesting is testing only bugs which were raised in last
version. 

regression testing is testing the entire functionality again
(including bugs).

Retesting is conducting for the improving confidence of
defect fixing means to identify that whether the defects is
being fixed or not

where as regression testing is identifying the side effects
of defect fixing means to identify that whether is there any
side effects came bcz of defect fixing..

regards
Sm