What term refers to a substance composed of many units?

The term that refers to a substance composed of many units is "polymer." Polymers are large molecules that are made up of repeating structural units, typically connected by covalent chemical bonds. These repeating units can be small molecules known as monomers, which bond together to form the larger structure.

In the context of nail care and manicure products, polymers are often used in formulations for their desirable properties, such as durability, flexibility, and resistance. They can be found in products like nail polishes, gels, and artificial nails, enhancing their strength and performance.

Monomers are the smaller units that join together to create polymers, while oligomers are similar to polymers but consist of smaller numbers of those units—usually just a few. A compound, on the other hand, refers to a substance formed from two or more different elements that are chemically bonded together, which does not specifically indicate the number of units involved. This makes "polymer" specifically suitable when discussing substances made from many repeated units.