What is the difference between verification and validation?

THE DISTINCTION BETWEEN THE TWO TERMS IS LARGELY TO DO WITH THE ROLE OF SPECIFICATION. VALIDATION IS THE PROCESS OF CHECKING WHETHER THE SPECIFICATION CAPTURES THE CUSTOMERS NEEDS,WHILE VERIFICATION IS THE PROCESS OF CHECKING THAT THE SOFTWARE MEETS THE SPECIFICATION.

•  verification means proving confirmation to the requirements by taking one or two trials 
• validation is a scientic approach providing evidence that the defined process will always result in expected Quality requirments, No of batches required depends on the process complexity. 

Verification profe the consistancy by External audit and Validation profe the consistancy by Internal Audit