An armhole is the opening in a shirt, dress, or jacket where your arm goes through. If you've ever put on a t-shirt and had to figure out which hole was for your head and which ones were for your arms, you were looking for the armholes.

The size and shape of armholes matter more than you might think. Armholes that are too tight make a shirt uncomfortable and restrict your movement. Armholes that are too large or cut too low can look sloppy or feel drafty. When a tailor makes a custom suit, they pay careful attention to where the armholes sit. Well-fitted armholes allow your arms to move freely while keeping the jacket looking sharp.

Sleeveless shirts and dresses still have armholes, they're just not covered by fabric. Some athletic clothing has larger armholes to allow more movement and ventilation during sports. Fashion designers sometimes create unusual armhole shapes to make garments distinctive or eye-catching.