Breathable describes materials that allow air and moisture to pass through them. A breathable jacket lets sweat vapor escape from your body while still protecting you from wind or rain. Cotton shirts are breathable because air can move through the tiny spaces between the fabric's fibers, keeping you cooler on hot days.

The opposite would be something like a plastic raincoat, which traps heat and moisture inside, making you feel clammy and uncomfortable. Breathable fabrics are especially important for athletic clothing, hiking gear, and anything you wear during physical activity. Modern outdoor gear often uses special breathable materials that keep rain out while letting your body's moisture escape, solving a problem that frustrated campers and athletes for generations.

The word can also mean suitable for breathing, like when scientists talk about whether a planet has a breathable atmosphere. Earth's air is breathable for humans, but the atmosphere on Mars isn't. In everyday conversation, though, you'll most often hear breathable used to describe clothing and fabrics that help you stay comfortable by letting your skin breathe.