finite
Having an end or limit; not going on forever.
Finite means having a definite end or limit. A finite amount of something will eventually run out. The cookies in a jar are finite: once you eat them all, they're gone. The minutes in a soccer game are finite: when the clock reaches zero, the game ends. Your summer vacation is finite: it lasts for a specific number of days before school starts again.
The opposite of finite is infinite, which means endless or unlimited. While the grains of sand on a beach might seem infinite, they're actually finite: you could count them if you had enough time. The universe itself might be finite or infinite, something scientists still debate.
Recognizing that something is finite can help you appreciate it. If you have a finite number of pages to write a story, you need to make every page count. If a video game gives you a finite number of lives, you play more carefully.