Duration

How long until that bond comes due? That's its duration.

Yeah, the concept is simple, but the better question revolves around why it matters. Loans which have a very long expiration (Disney has issued 100-year bonds) are volatile. Like...you issue a 30-year bond paying 5% interest. You're in year 3 of the 30—that is, you have 27 more years of paying rent on that money—and with a globally weak economy, the central banks of the world have dropped rates dramatically. Your same-risk bond would cost only 3 1/2% interest today—sadly for you, you have no call feature wherein you could buy back your existing 5% bond and refinance it way cheaper.

So after you fire your CFO, you think about the edge cases here that frame just how much money this call feature will cost you (think: 1.5% per year for 27 years on however much money you borrowed—like, if it was $100 million, just by not adding that paragraph on callability, it cost you $1.5 million a year.) Anyhoo, think about the other end of the borrowing duration spectrum—had your duration been only one year, and rates suddenly dropped massively as outlined, you'd "only" have lost $1.5 million—and probably less than that, as the cost of refinancing is meaningful and a lot of hassle, and you probably would have just suffered for that one year and been done with it.

But in this case with a very long duration, under the new rates of 3.5%, your 5%-interest-paying bond would be prized dearly, and its $1,000 par value would likely carry a market value of something like $1,500. The long duration of the bond made it extremely volatile. Way more volatile than the conversation you had with your CFO as he carried out his little cactus plant and family pictures on the way to his car.