"Dense" refers to a substance that has a high mass relative to its volume. This means that a dense material contains a lot of matter packed into a small space. For example, metals like lead and gold are considered dense because they are heavy for their size, making them feel solid and substantial. In contrast, a less dense material, like foam or air, has less mass in the same volume, making it lighter and often more buoyant. Density is an important property in various fields, including physics, engineering, and materials science, as it affects how substances interact with each other.