Question

What is interest?

Answer 1

the feeling of a person whose attention, concern, or curiosity is particularly engaged by something:
She has a great interest in the poetry of Donne.

OR

DEFINITION of 'Interest' 1. The charge for the privilege of borrowing money, typically expressed as an annual percentage rate. 2. The amount of ownership a stockholder has in a company, usually expressed as a percentage.

If it's not any of these your looking for try a dictionary.. :)