A reminder is something that helps you remember to do something or prompts you to think about something you might have forgotten. When your mom leaves a note on the refrigerator saying “dentist appointment at 3:00,” that's a reminder. When your phone buzzes to tell you it's time to start your homework, that's a reminder too.

Reminders can take many forms: a string tied around your finger, an alarm on your watch, a calendar notification, or even another person saying “Don't forget to bring your permission slip tomorrow!” Some people set reminders for themselves by writing to-do lists or keeping a planner.

The word can also mean something that brings a past experience or fact back to your mind. An old photograph might serve as a reminder of a great vacation. The scar on your knee might be a reminder of the time you fell off your bike learning to ride without training wheels.

People often say “just a friendly reminder” when they want to help someone remember something without sounding bossy or critical. The key thing about reminders is that they're helpful tools: they work with your memory, not against it, helping you stay organized and keep track of what matters.