dense

Dense is an adjective describing something tightly packed, thick, or closely spaced, with high mass per unit volume. It can also refer to something difficult to see through or understand, such as dense fog or a dense text. In everyday language, dense can describe physical material as well as metaphorical complexity.

In physics, density is the property of matter defined as mass per unit volume. It is an intrinsic property of a substance, independent of the amount present. The common unit is kilograms per cubic meter (kg/m^3), though grams per cubic centimeter (g/cm^3) is frequently used in everyday contexts. Temperature and pressure affect density: most substances expand with heat, reducing density, while cooling or compression increases density.

Population density measures how many people live in a given area, typically expressed as persons per square kilometer or square mile. It is used in urban planning, epidemiology, and regional geography to compare living concentration across regions or cities.

In mathematics and computer science, dense has specialized meanings. A dense matrix contains a high proportion of nonzero entries, as opposed to a sparse matrix. A dense graph has many edges relative to the number of vertices. Densities are expressed as ratios, such as the fraction of nonzero entries in a matrix or the ratio 2|E|/(|V|(|V|-1)) for a simple graph.

Etymology: dense comes from Latin densus meaning thick, through Old French desne/dense, entering English in the medieval period.