Accretion is the ongoing increase in the earnings and assets of a business, due to its continuing expansion. Accretion can occur due to organic growth or from the acquisition of other entities. Accretion is also an accounting term, referring to the gain generated by an investor after a bond has been purchased at a discount. By holding the bond until its maturity, the investor gradually earns a profit on the difference between the discounted purchase price and the face value of the bond.