Adhesive, more commonly referred to as glue, is any one of multiple substances which, when applied to two surfaces, will bond or seal them and resist separation pressure.
There are two broad categories of glue – natural and artificial. Most modern adhesives are artificial but glue of various kinds has been used for hundreds of years. Synthetic adhesives have plenty of advantages over natural adhesives, including consistency, bond strength, and adaptability.
Modern adhesive is made from a variety of carefully engineered chemical substances. Adhesives are characteristically organised by adhesion methods. These are then further separated to define reactive and non-reactive adhesives, referring to if the adhesive undergoes a chemical reaction to harden. Common types of adhesives include epoxy, silicone, and acrylic.