Defining machine learning is not a simple matter; to do that, we can start from the definitions given by leading scientists in the field:
"Machine Learning: Field of study that gives computers the ability to learn without being explicitly programmed." – Arthur L. Samuel(1959)
Otherwise, we can also provide a definition as:
"Learning denotes changes in the system that are adaptive in the sense that they enable the system to do the same task or tasks drawn from the same population more efficiently and more effectively the next time." ...