Accrual Period
The time interval over which bond interest accumulates — typically from one coupon date to the next.
The accrual period is the window during which interest 'accrues' on a bond. For a bond paying semi-annual coupons on June 1 and December 1, the accrual period from June 1 to December 1 is 183 days (or 6 months, depending on day count convention). If you buy the bond on September 1 (3 months after the last coupon), you owe the seller accrued interest for those 3 months. Think of it as rent for the bond: every day you hold the bond, you earn a little interest. The accrual period resets on each coupon date. Day count conventions (30/360, Actual/365, Actual/Actual) determine exactly how many days count in each period, which affects accrued calculations.
Current Yield
Annual coupon income divided by the bond's clean price.
Running Yield
Annual coupon income divided by the bond's dirty price (clean price plus accrued interest).
Yield to Maturity (YTM)
The annualized return if you hold the bond to maturity, assuming all coupons are reinvested at the same rate.
Dirty Price
The total settlement price paid for a bond, including accrued interest.
Clean Price
The quoted bond price excluding accrued interest.
Accrued Interest
Interest that has accumulated since the last coupon payment, paid by the buyer to the seller.