Gum

Gum, sticky substance from plants that hardens when dry. Gum arable is obtained from certain African acacia trees. It is used as an adhesive on envelopes and postage stamps. Gum guaiacum, from the lignum vitae tree, is used for treating gout and for detecting bloodstains, which cause it to change color. Chewing gum comes from the sap of the sapodilla tree.