An adhesive is a compound which is used in order to adheres or bonds two items together.
Adhesives may come from either natural or synthetic sources.
Natural adhesives, Synthetic adhesives, Drying adhesives, Contact adhesives, Hot adhesives (thermoplastic adhesives), Reactive adhesives, UV and Light Curing Adhesives, Pressure sensitive adhesives are different types of adhesives.
The strength of attachment between an adhesive and its substrate depends on many factors.
Adhesion may occur either by mechanical means, in which the adhesive works its way into small pores of the substrate, or by one of several chemical mechanisms.