To prove something to be sound or logical. Also to certify conformance to a standard. Contrast with "verify," which means to prove something to be correct.

For example, data entry validity checking determines whether the data make sense (numbers fall within a range, numeric data are all digits, etc.), but "validity" checking does not "verify" that the data are correct. Even if the check digit in a customer account number is determined to be a valid number, it may still be the wrong number for that individual. In practice however, the terms "validate" and "verify" are often used synonymously. See validity checking, check digit and HTML validator.

Errors Can Be Laughable
Validating data typed into the computer is not a complicated concept. However, with regard to proper names, if there is no existing database to compare to, validation is a time-consuming job. The only way to ensure correct spelling is to have two different operators type the same name twice or to have a person visually compare what has been typed by another.