(uncountable) (finance) The price paid for obtaining, or price received for providing, money or goods in a credit transaction, calculated as a fraction of the amount or value of what was borrowed. [from earlier 16th c. –
Our bank offers borrowers an annual interest of 5%.
(uncountable) A great attention and concern from someone or something; intellectual curiosity. [from later 18th c. –
He has a lot of interest in vintage cars.
(uncountable) Attention that is given to or received from someone or something.
(countable) A business or amorous link or involvement.
I have business interests in South Africa.