Stale describes food that has lost its freshness and appealing qualities from sitting out too long. When bread becomes stale, it feels hard and dry instead of soft. Stale cookies lose their crisp snap or chewy texture. The word describes food that's old enough to have changed for the worse, though it's usually still safe to eat.

But stale describes ideas, performances, and other non-food things too. Ideas can become stale when they've been repeated so many times that they feel tired and boring. A comedian's jokes might go stale after the hundredth telling. A teacher might worry that her lessons feel stale if she teaches exactly the same way year after year without bringing in fresh examples or new approaches.

Air can also be stale. When you walk into a room that's been closed up for weeks, you might notice the air smells musty and stale, lacking the freshness of air that's been circulating. Opening a window lets in fresh air to replace stale air.

The opposite of stale is fresh: fresh bread, fresh ideas, fresh air. When something goes stale, it hasn't necessarily gone bad, but it has definitely lost what made it interesting or appealing in the first place. That's why bakers work through the night to have fresh bread ready each morning, and why writers keep searching for new ways to express old truths.