English Reference
noun

density

n.
US /ˈdɛnsəti/ UK /dˈɛnsɪti/ den·si·ty UK spelling densities, density's

  1. 01 B2 Upper Intermediate Technical Science

    how heavy or thick a substance is for its size.

    the mass per unit volume of a substance. Uncountable in a general scientific context but countable when referring to specific values.

    Simple

    Lead has a much higher density than aluminium, which is why it feels so heavy.

    In context

    The scientist calculated the density of the unknown alloy by measuring its displacement in water and comparing it to its dry mass.

    thicknesscompactnesssolidity
  2. 02 B2 Upper Intermediate

    the number of people or things in a specific area.

    the number of individuals or units per unit of area, such as population per square kilometre.

    Simple

    The population density in the city centre is much higher than in the countryside.

    In context

    Urban planners are concerned that increasing the housing density without improving public transport will lead to severe traffic congestion.

    sparseness
  3. 03 C1 Advanced AcademicTechnical Math

    the likelihood of a value falling within a certain range.

    the relative likelihood of a continuous random variable taking on a given value; the derivative of the cumulative distribution function.

    Simple

    The graph shows the probability density of the test scores.

    In context

    In a normal distribution, the probability density is highest at the mean and tapers off symmetrically toward the tails.

  4. 04 C2 Proficiency InformalHumorous

    the quality of being slow to understand something.

    a figurative extension of 'thickness' referring to a person's inability to comprehend simple concepts or instructions.

    Simple

    I explained it three times, but his density is sometimes quite surprising.

    In context

    Despite the obvious clues left by the investigators, the suspect's sheer density prevented him from realising he was being trapped.

    stupidityslowness

Usage low density

In truth, this hugely uneven population density is bad for both sides.

The Local· 14 Aug 2026

Using orbital data from roughly 1,200 Starlink satellites, they reconstructed changes in atmospheric density about 500 kilometers above Earth.

ScienceDaily· 12 Aug 2026

Borrowed from Middle French densité or Latin densitas. Morphologically dense + -ity.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin densitas
Level C1 · Advanced
Frequency Common
Updated