There are a large number of adhesive types for various applications.  They may be classified in a variety of ways depending on their chemistries (e.g. epoxies, polyurethanes, polyimides), their form (e.g. paste, liquid, film, pellets, tape), their type (e.g. hot melt, reactive hot melt, thermosetting, pressure sensitive, contact, etc.), or their load carrying capability (structural, semi-structural, or non-structural).

Structural adhesives refer to relatively strong adhesives that are normally used well below their glass transition temperature, an important property for polymeric materials, above which polymers are rubbery and below which they are glassy.  Common examples of structural adhesives include epoxies, cyanoacrylates, and certain urethanes and acrylic adhesives.  Such adhesives can carry significant stresses, and lend themselves to structural applications.