any of a class of substances belonging to the family of organic polymers (polymer), prepared by heating urea and formaldehyde in the presence of mild alkalies, such as pyridine or ammonia. The urea and formaldehyde undergo a condensation reaction in which they combine to form a water-soluble polymer. This polymer is used to formulate adhesives and coating agents or is mixed with wood fibre, pigments, and other substances to produce powders that can be molded into solid objects. Under the influence of heat and pressure, further reactions occur that can convert the polymer into a moisture- and heat-resistant resin. The molecular structure of the final product is that of a three-dimensional network resembling those of resins made by the reaction of formaldehyde with phenol or with melamine.

Different types of urea–formaldehyde resins are used in making molded articles, such as buttons, tableware, and housings for apparatus, and in adhesives, lacquers, and agents that render textiles resistant to creasing or crushing.