Adhesive

An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together.

Nitrocellulose adhesive outside a tube

Adhesives may come from either natural or synthetic sources. Some modern adhesives are extremely strong, and are becoming increasingly important in modern construction and industry. The types of materials that can be bonded using adhesives are virtually limitless, but they are especially useful for bonding thin materials. Adhesives usually require a controlled temperature to cure or set. They can be electrically and thermally conductive or non-conductive. The earliest date for a simple glue is 200,000 BC and for a compound glue 70,000 BC.