"Hardener" Natural Recordings by Native Speakers
A hardener is a substance or agent that hardens or strengthens something, such as a material or a bond. For example, a hardener might be added to a liquid mixture to make it set and become rigid, or it might be used to bond two surfaces together more effectively. Common uses of hardeners include in construction materials, adhesives, and encapsulations.
A hardcover is a type of book binding that covers the book's pages with a hard material, usually made of cardboard or rigid plastic, and is often covered with a paper or cloth wrapper. Hardcovers are typically more expensive and durable than paperback books, and are often considered to be of higher quality.