# When to use which zero curves

I have a very basic question. Why are there many different zero curves for a given currency/market? For example, there are zero curves constructed using gov bonds, swaps, STIR futures, OIS, Inflation, currency basis, etc. When would you use which zero curve?

Furthermore, there are different tenors, e.g. 1M Zero, 3M Zero, etc. When would you use which?

Will you use bond derived z curve when pricing bonds, and swap derived when pricing swaps?

Will you use 1M Zero when pricing swaps where the reference rate is 1M rate?

• To discount a cash flow at time T, you need the discount rate $r(0,T)$. Zeros have a nice property. You know that from their pricing formula $YtM=r(0,t)$. Although, from a bullet bond, the yield to maturity cannot be mapped to a discount rate. Because it's YtM is an "imaginary" metric since you cannot reinvest in it – alexbougias Jun 11 '19 at 11:47