density

noun

den·​si·​ty ˈden(t)-sə-tē 

plural densities

1

: the quality or state of being dense

measures of traffic density

the density of the cake

felt that the candidate's density on the subject of equality was alarming

the density of her prose

2

mathematics : the quantity per unit of volume (see volume entry 1 sense 2), unit of area (see area sense 1), or unit of length: such as

a

chemistry : the mass (see mass entry 2 sense 1c) of a substance per unit of volume

pure iron has a density of 7.8 grams per cubic centimeter

b

chemistry : the distribution of a quantity (such as electricity or energy) per unit usually of space (such as length, area, or volume)

The drawback to using ethanol as a complete replacement for gasoline, however, is not only the high cost of its production from cellulose but also its lower energy density.

—John R. Regalbuto

c

: the average number of individuals or units per unit of space

a population density of 500 per square mile

a housing density of 10 houses per acre

3

physics

a

: the degree of opacity (see opacity sense 2) of a translucent medium

the fog's density

b

: the common logarithm of the opacity

Synonyms of density

• consistency
• consistence
• thickness

Examples of density in a Sentence

We were surprised by the fog's density.

the density of her writing style

These instruments are used for measuring the density of the atmosphere.

Recent Examples on the Web

The Thai capital doesn't have an Old Town like Hanoi, the modernity of Hong Kong, or the density of temples like Siem Reap (though few places in Southeast Asia are as spectacular as Wat Arun at sunrise). —Chris Schalkx, Condé Nast Traveler, 21 Feb. 2026

While it could, theoretically, be used in things like phones, such batteries have lower energy densities and may not be appropriate in the long run. —Christopher McFadden, Interesting Engineering, 21 Feb. 2026

The lawsuit follows similar sentiments that neighbors at The Timbers shared during both the Planning Commission and City Council meetings, to which McCullough responded by saying that the density of the project is considered a low-density project, the same as neighboring communities. —Taylor O'Connor, Kansas City Star, 20 Feb. 2026

Over the past decade, battery costs have dropped by roughly 90%, while energy density has doubled. —New Atlas, 20 Feb. 2026

Word History

Etymology

see dense

First Known Use

1598, in the meaning defined at sense 1

Phrases Containing density

• density function
• high-density lipoprotein
• low-density lipoprotein
• population density
• probability density
• probability density function
• very low density lipoprotein

Rhymes for density

• immensity
• intensity
• propensity

Kids Definition

density

noun

den·​si·​ty ˈden(t)-sət-ē 

plural densities

1

: the quality or state of being dense

2

: the quantity of something per unit volume, unit area, or unit length: as

a

: the mass of a substance per unit volume

density expressed in grams per cubic centimeter

b

: the average number of individuals or units in a unit of area or volume

a population density of 500 per square mile

3

: stupidity sense 1

Medical Definition

density

noun

den·​si·​ty ˈden(t)-sət-ē, -stē 

plural densities

1

: the quantity per unit volume, unit area, or unit length: as

a

: the mass of a substance per unit volume

b

: the distribution of a quantity (as mass, electricity, or energy) per unit usually of space

c

: the average number of individuals or units per space unit

a population density of 500 per square mile

2

a

: the degree of opacity of a translucent medium

b

: absorbance