Functionality testing is nothing but Black box testing

Functional Testing is the major part of  Black box testing 
in which the functionality of the AUT should be tested. 
Where as Black Box Testing means testing the application 
based on its performance with out concerning its internal 
design.

Hai,
according to me 
Blockbox testing is the testers test the app without any 
knowledge of internal design of code i.e called as B.T
Functionality Testing means
similar to blockbox testing 
but here we check whether the functionlites of app working 
properly r not.
here we wont consider the internal structure.