Tile is a flat piece of hard material used to cover surfaces like floors, walls, or roofs. Most tiles are made from baked clay, stone, or ceramic, though modern tiles can be made from glass, metal, or even plastic. They come in many shapes and sizes: square bathroom tiles might be just a few inches across, while roof tiles can be a foot long or more.

People have used tiles for thousands of years because they're durable, waterproof, and easy to clean. Ancient Romans created elaborate mosaic floors by arranging thousands of tiny colored tiles into pictures and patterns. Today you'll find tiles in bathrooms and kitchens because water beads up on their smooth surface instead of soaking in. Swimming pools are lined with tiles that won't deteriorate in chlorinated water.

The word also appears in games and computers. In Scrabble, players arrange letter tiles to form words. A tiled window on a computer screen means multiple windows arranged side by side without overlapping, like tiles fitted together on a floor. And when you tile something, you're covering it with tiles or arranging things in a tilelike pattern.