Periodic means happening at regular intervals or repeating in a predictable pattern. If your school has periodic fire drills, they happen at set times throughout the year, maybe once every few months. When a comet makes periodic visits to our solar system, it returns on a reliable schedule, like Halley's Comet appearing roughly every 76 years.

Something periodic doesn't happen randomly or just once: it follows a rhythm or cycle you can count on. Magazine subscriptions are periodic because issues arrive regularly, whether weekly, monthly, or quarterly. Your heartbeat is periodic, with each pulse following the last in steady time.

In science class, you might encounter the periodic table, which organizes chemical elements in repeating patterns based on their properties. Elements in the same column share similar characteristics, and this pattern repeats across rows.

The opposite of periodic would be random or one-time. Rain in your town might be periodic if it comes reliably each afternoon during summer, but sporadic (irregular and unpredictable) if storms arrive without any pattern. A periodic drip pauses between drops in a regular rhythm.