density
Pluraldensities
- 1A measure of how much mass is contained in a given unit of volume.
Engineers compared the density of several alloys before choosing the lightest one.
Seawater has a slightly higher density than fresh water because of the dissolved salts.
Note
The physicist's sense, borrowed from Middle French densité or Latin densitas and shaped like dense + -ity. It is given as mass over volume, as in water's 1 kg/L, and it takes a plural when materials are compared: exoplanet densities ranging from styrofoam to iron. When precision matters, the field says mass density, which keeps it apart from counts spread over space.
- 2A ratio relating an amount of something to the space, area, or extent over which it is spread.
Urban planners track population density to decide where new schools are needed.
The forest's tree density dropped sharply in the years after the wildfire.
Similarconcentration
Oppositesparseness, sparsity
Note
Almost always paired with a noun naming what is counted: particle density, keyword density, hair density measured in strands per square inch. The space can be a page of text, a scalp, or a stretch of town where a business has customers, so the word travels easily into hairdressing, marketing and search-engine writing. Scientists say number density when they need to separate it from the mass-per-volume measure.
- 3The relative likelihood that a continuous random variable takes a given value, expressed as probability per unit of the range.
The analyst plotted the density to see where the measurements clustered.
For a normal distribution, the density peaks at the mean and tapers toward the tails.
Note
In statistics the word names a rate rather than a chance. It is probability per unit of range, so a single value of the density is not itself a probability; a probability comes only from an interval. Written out in full it is probability density, the form to choose when the general spread-over-space ratio might otherwise be understood.
Less common meaning
- 4Slowness or dullness of mind; stupidity.
The foreman despaired at the density of his new apprentice, who grasped nothing he was shown.
Her density in matters of money cost the family dearly over the years.
Similarstupidity, obtuseness, dullness, slowness, thickness
Oppositeintelligence, cleverness, brightness, sharpness
Note
An older figurative use, now dated, in which a mind is thick the way a substance is. Today it sounds old-fashioned or deliberately arch, and denseness says the same thing with less risk. In any scientific setting it is easily misread as the physical measure, so it is safest in period writing or playful description.
Practice
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Origin
This word was borrowed from Middle French "densité" or Latin "densitas," and is formed from "dense" plus the suffix "-ity."