If you’re overdue for a trip to the gym, be careful not to overdo it on the exercise when you get there — otherwise you’ll be sore. Anything overdue should’ve happened already, but to overdo something is to do too much of it.

A library book or a cable bill is overdue when it’s late. Anything that is long overdue has taken too long to happen, like justice or positive change. Haven’t sent thank-you notes from last year’s birthday party? They’re definitely overdue! Luckily, these examples aren’t overdue:

Such a change is long overdue, and would be welcome news. (Washington Times)

Once a patron has used up their three renewal periods, they will have 45 days to return an overdue book. (Los Angeles Times)

To overdo, on the other hand, is to do more than is necessary. To do something is good; to overdo it is bad. We won’t overdo it, but here are a couple of examples:

The French don’t deprive themselves of delicious desserts — but they also don’t overdo it. (Washington Post)

Don't overdo it, though—willpower can get depleted if you try to exercise it too much. (Scientific American)

Overdue is an adjective, like that overdue library book you keep forgetting to return. Overdo is a verb. Don’t overdo it by causing a scene if someone gets these two words mixed up!