Incidental means happening as a minor part of something else, not as the main purpose or focus. When something is incidental, it occurs alongside the important stuff but isn't the reason things are happening.

If your family takes a trip to visit your grandmother and you happen to see a cool museum along the way, the museum is an incidental part of the trip. You didn't travel for the museum, but you enjoyed it anyway. When a scientist studies migration patterns of birds and notices something interesting about their feathers, that observation might be an incidental finding from her research.

The word often appears in the phrase incidental expenses, meaning small costs that come up unexpectedly during a bigger activity, like buying a snack during a field trip you'd already paid for. These expenses aren't planned or central; they just happen along the way.

Incidental is related to the word incident, which means an event or occurrence. Something incidental is connected to the main event but not essential to it. The opposite might be fundamental or essential, things that really matter to the core purpose. Understanding what's incidental versus what's essential helps you focus your energy on what actually matters most.