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

Combined oral contraceptives also may have side effects related to bone density that need to be studied in space, as the authors noted in the new study. —Jessica Rendall, Space.com, 7 Dec. 2025

Known as ironwood due to its wood density, its autumn foliage is a distinctive trait. —Joshua Siskin, Oc Register, 6 Dec. 2025

Exercise can increase bone mineral density in postmenopausal women and older adults, reducing fracture risk, and high-intensity resistance training is one of the most effective activities for improving bone health, studies have shown. —Dana Santas, CNN Money, 5 Dec. 2025

High power, fast cycling Grid services like frequency regulation require batteries that excel in power rather than energy density. —Neetika Walter, Interesting Engineering, 5 Dec. 2025

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