The yield contribution of issuing a loan below par, amortized over the loan's expected life. Using the source's yield-to-takeout convention y_t ≈ y_c + (Par-Price)/(n · Price), a 99 OID on a loan with a 3-year expected life adds roughly 34 bps to all-in yield; on a 4-year expected life, roughly 25 bps. OID is one of three pricing components alongside the floating-rate index and the contractual spread.