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Name the object of each description
A supplied spot curve contains a factor or rate for multiple maturities on a specified basis. A YTM belongs to one price and promised payment schedule. It can be used to reproduce that price under its quotation convention, but does not by itself specify every separate zero price.
Compare the required inputs
| Feature | Spot curve | Single YTM |
|---|---|---|
| Discounting | Payment-date-specific factors | One convention-matched rate |
| Input association | Dates on a common curve | One security price and schedule |
| Nonflat curve | Preserved | Compressed for this schedule |
| Another coupon mix | Reuse dated factors if basis matches | Solve another fitted yield |
Use a zero as the special-case check
For one final payment, the fitted yield and maturity-matched spot rate agree on the same basis. Adding earlier coupons changes the price equation. This helps explain why the equality for a zero is not a general coupon-bond rule.
Choose the representation for the task
Use the supplied curve when the task asks for dated no-arbitrage valuation or curve scenarios. Use a stated YTM when the task deliberately provides a single-rate price model. Neither label removes the need to check payment dates, compounding, credit and optionality assumptions.