Merriam-Webster Collegiate Dictionary - interest

 I. noun  Etymology: Middle English, probably alteration of earlier interesse, from Anglo-French & Medieval Latin; Anglo-French, from Medieval Latin, from Latin, to be between, make a difference, concern, from inter- + esse to be — more at is  Date: 15th century  1.  a.  (1) right, title, or legal share in something  (2) participation in advantage and responsibility  b. business, company  2.  a. a charge for borrowed money generally a percentage of the amount borrowed  b. the profit in goods or money that is made on invested capital  c. an excess above what is due or expected returned the insults with ~  3. advantage, benefit; also self-~  4. special ~  5.  a. a feeling that accompanies or causes special attention to an object or class of objects ; concern  b. something that arouses such attention  c. a quality in a thing arousing ~  II. transitive verb  Date: 1608  1. to induce or persuade to participate or engage  2. to engage the attention or arouse the ~ of