Density (noun)

1. The measure of mass per unit of volume of a substance or object.
2. The amount of something per unit of area or unit of volume.

Origin:

From the latin word 'densus' meaning 'thick' or 'close together'.

Examples:

1. The density of the metal was determined by a precise measurement of its mass and volume.
2. The population density of the city was much higher than in the surrounding rural areas.
3. The density of the traffic was so heavy that it took almost an hour to travel just a few miles.
4. The research showed that the density of the forest had increased over the past decade.
5. The density of the book was measured by counting the number of pages and dividing by the weight.