A fastening is anything that holds two things together or keeps something closed. When you zip up your jacket, button your shirt, or buckle your seatbelt, you're using a fastening. The snap on your jeans, the clasp on a necklace, the Velcro on your shoes: these are all fastenings.

Different fastenings work in different ways. A button slides through a buttonhole and gets caught there. A zipper uses tiny interlocking teeth that mesh together when you pull the slider up. Safety pins pierce through fabric and lock closed. Paper clips grip pages by bending around them.

People have invented hundreds of types of fastenings over thousands of years, each designed for specific needs. Climbers use carabiners (metal clips) as fastenings for their ropes because they need something incredibly strong and reliable. Surgeons use special fastenings to close incisions after operations. Carpenters use nails and screws as fastenings to hold wood together.

The verb form is fasten, meaning to close or attach something using a fastening: “Please fasten your seatbelt before we start driving.”