Which amount of time is inexact? a while an hour

"A while" is inexact because it refers to a period of time that can vary greatly depending on context—sometimes it’s a few minutes, other times it might be hours. It’s like saying, “I’ll be back in a bit!”—but nobody really knows what “a bit” means! On the other hand, "an hour" is specific. When you say “an hour,” you're clearly indicating a fixed duration of 60 minutes. So if someone asks you how long you’ll be gone, saying “an hour” gives them a much clearer expectation than “a while.”