A windowsill is the flat, horizontal ledge at the bottom of a window, both inside and outside a building. If you've ever set a potted plant by a sunny window or rested your arms while looking outside, you were probably using the windowsill.

Inside your home, the windowsill creates a perfect spot for displaying small objects, growing herbs that need sunlight, or watching rain streak down the glass. Cats famously love to curl up on sunny windowsills, soaking up warmth while keeping an eye on birds outside. Outside, the windowsill helps direct rainwater away from the wall so it doesn't damage the building.

You might also hear it called a window ledge. In older buildings, windowsills were often made from a single piece of stone or thick wood, while modern ones might be made of plastic, metal, or composite materials. Whether you're setting down a book, arranging flowers, or just gazing out at the world, the windowsill is that familiar perch where the inside meets the outside.