Clean Price vs Dirty Price
Also called: clean price, dirty price, full price
The clean price is a bond's price excluding accrued interest; the dirty price is what you actually pay. Bonds are quoted clean because the clean price moves smoothly with yields, while the dirty price sawtooths upward between coupon dates and drops each time one is paid. Confusing the two is a classic settlement error, and it's why a bond can look like it fell 2% on a day when nothing happened but a coupon.
Formula
Dirty price = Clean price + Accrued interest