Definition:

Interest is a payment made to a lender or other creditor as a charge for the use of money borrowed or for the delay in payment of a debt. It is typically calculated based on the principal amount, the interest rate, and the time period.

Types of Interest:

• Simple interest: Interest calculated on the principal amount only, without compounding.
• Compound interest: Interest calculated on the principal amount and accumulated interest from previous periods.
• Prime interest: The federal funds rate set by the U.S. Federal Reserve.
• Discount interest: Interest paid in advance on a loan to reduce the cost of borrowing.
• Interest charge: A fee charged for the use of credit or the provision of credit services.

Formula for Simple Interest:

I = P * r * t

where:

• I is the interest amount
• P is the principal amount
• r is the interest rate (expressed as a decimal)
• t is the time period (in years)

Formula for Compound Interest:

A = Pe^(rt)

where:

• A is the future value of the investment
• P is the principal amount
• e is the base of the natural logarithm
• r is the interest rate (expressed as an annual rate)
• t is the time period (in years)

Factors Affecting Interest:

• Principal amount
• Interest rate
• Time period
• Compound or simple interest

Examples:

• A loan of $10,000 for 5 years at an interest rate of 3%. The simple interest calculated is $1,500.
• A savings account with a balance of $5,000 earning interest at a rate of 2%. The compound interest earned after 2 years is $1,000.

Additional Notes:

• Interest is a passive income, meaning it is income earned without actively doing anything.
• Interest rates are regulated by central banks in most countries.
• Interest can be paid on a variety of assets, including loans, savings accounts, and investments.