An accessory is something you add to make something else more useful, attractive, or complete. When you buy a new phone, accessories might include a case, headphones, or a charging cable. These extras aren't essential for the phone to work, but they enhance it.

In fashion, accessories are items like belts, hats, scarves, jewelry, or bags that complete an outfit. A simple dress becomes more interesting with the right accessories. Baseball players wear uniforms, but accessories like batting gloves, wristbands, and eye black help them perform better or express their style.

The word also appears in law with a serious meaning: an accessory to a crime is someone who helps another person commit a crime, either before it happens or by helping them escape afterward. This person didn't commit the main crime but knowingly assisted the criminal. Being an accessory is itself a crime because you're helping something wrong take place.

Notice how in every case, an accessory is secondary to something else. It's the supporting player, not the star. A bike is the main thing; the bell and water bottle holder are accessories.