system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we use Half-Life for elements and not Quarter-Life or any other fraction?
gpt
Nuclear physicists use half-life (time it takes for number remaining to halve). Particle physicists often use the mean lifetime instead, which is the time it takes for the sample to drop by a factor of 1/e.

In principle we could use any other (nonzero) fraction. It's just convention. 1/2 is an easy fraction to visualize, it's easy to calculate powers of 2 in your head, etc.