the spatial property of being crowded together
"The apartment building was so dense that we could barely see each other's faces from our windows."
A measure of the mass of matter contained by a unit volume.
"The high density of the lead weights made them sink immediately to the bottom of the pool."
In plain English: Density is how much stuff is packed into a specific amount of space.
"The high density of the city made it difficult to find parking."
Usage: Use density to describe how tightly packed the mass of a substance is within a specific space. It applies to physical materials like water or air rather than abstract concepts or group sizes.
The word density comes from the Latin term densitas, which was borrowed into English via Middle French. It is formed by combining the root for "dense" with a suffix meaning "the state of."