When a needle pulls thread through fabric and into a loop, that's a stitch. Every quilt, no matter how elaborate, starts with a single stitch.
You can stitch a design on a pillow, or stitch up a hole in your jeans using stitches. Doctors sometimes stitch up patients' skin, too — if you cut yourself badly enough, you might need stitches. Another kind of stitch is a painful cramp in your stomach or side: "I stopped running when I got a stitch." If someone says, "I haven't got a stitch to wear," they're short on clothing. And being "in stitches" means laughing uncontrollably.