Gum is the pink tissue in your mouth that surrounds and supports your teeth. Healthy gums fit snugly around each tooth like a turtleneck collar, protecting the roots and helping hold everything in place. When you brush your teeth, gently brushing your gums too can help keep them healthy. If gums get infected or damaged, teeth can become loose or painful.

The word also refers to the sticky, chewy substance you might get from a gumball machine. Chewing gum is made from synthetic rubber or natural tree sap mixed with sweeteners and flavors. People have been chewing gum for thousands of years: ancient Greeks chewed resin from mastic trees, while ancient Mayans chewed chicle from sapodilla trees.

Gum can also mean a sticky substance that oozes from certain trees. When a tree gets damaged, it sometimes produces gum to seal the wound, like how your body makes a scab over a cut. Some trees produce so much gum that people harvest it: gum arabic, which comes from acacia trees, is used in foods, art supplies, and even postage stamps.