The rate of interest per cent refers to the percentage of the principal amount that is charged or earned as interest over a specific period of time. It is commonly used in financial transactions such as loans, investments, and savings accounts. For example, if a loan has an interest rate of 5% per annum, it means that the borrower will be charged 5% of the loan amount as interest each year. Similarly, if a savings account offers an interest rate of 2% per annum, it means that the account holder will earn 2% of the account balance as interest each year.