Interest

n.
  1. Excitement of feeling, whether pleasant or painful, accompanying special attention to some object; concern; a desire to learn more about a topic or engage often in an activity.
  2. (Finance, Commerce) Participation in advantage, profit, and responsibility; share; portion; part; as, an interest in a brewery; he has parted with his interest in the stocks.
  3. Advantage, personal or general; good, regarded as a selfish benefit; profit; benefit.
  4. (Finance) A fee paid for the use of money; a fee paid for a loan; -- usually reckoned as a percentage; as, interest at five per cent per annum on ten thousand dollars.
  5. Any excess of advantage over and above an exact equivalent for what is given or rendered.
  6. The persons interested in any particular business or measure, taken collectively; as, the iron interest; the cotton interest.
    7. Compound interest ,
    interest, not only on the original principal, but also on unpaid interest from the time it fell due.
    Simple interest ,
    interest on the principal sum without interest on overdue interest.