They are more or less the same thing. Yield is more specific to the lender/investor context. So when you take on debt, you pay an interest rate. When you invest in debt, you examine the yield. Or when you look back on investment performance (which can also apply to stocks, i.e. dividend yield and earnings yield), you’ll examine the yield on your investment. The difference is that in fixed income, you have more certainty (though not complete certainty) about what the cash flows are going to be, so you will find yourself analyzing what the yield on an investment will be if there is no default (or sometimes no option exercise). An interest rate is more generic. The interest rate is what you pay on debt, and sometimes it will simply mean the coupon rate on a bond, which can be different from the yield (if the bond is not trading at par, for example). So the answer is that they tend to mean pretty similar things, but there are some contexts in which interest rate is not a specific enough term. Yield has a more precise investment meaning, which is why it tends to be used for situations where you are investing in debt instruments, whereas interest rates are used more when a) you are borrowing money, or b) when you are talking about the state of the macroeconomy.
^^^^^ all of the above Excluding most money market securities blah blah blah… Yield includes capital gain or loss, interest rate generally does not. “From an investor point of view” this has tax & call implications.