What you gain with age (and something that seems to have eluded us here at Shmoop).
Also, the date when a debt becomes due for paying up.
Example
You buy a $1,000 bond with a maturity date of May 5. You’re basically buying a little bit of a company's debt. So what happens on May 5? That's the date you’ll get your 1G back—and you’ll have the interest you've earned on the bond, too.