dense

Formsdenser, densest

1. 1
   adjective

   Compact and tightly crowded together into a small space.

   The city's dense neighborhoods pack thousands of people into a few blocks.

   Mangrove roots grow so dense that boats cannot pass between them.

   Similarpacked, crowded, compact, thick, tight

   Oppositediffuse

   Note

   Here the crowding is of separate things, such as people, houses or roots, rather than of matter itself as in the mass-per-volume sense. Its most familiar partner is population. The New Encyclopaedia Britannica of 1998 speaks of "the regions of densest population" along the Huai. Compact, crowded and packed are its near neighbors, and like them it takes the superlative easily.

2. 2
   adjective

   Having a comparatively high density, with much mass contained in a small volume.

   Neutron stars are extraordinarily dense, packing huge mass into a tiny sphere.

   Lead is denser than aluminum, so equal volumes differ greatly in weight.

   Similarsolid

   Note

   The physical sense behind the rest. English took the word through Middle French from Latin dēnsus, "thick," from an Indo-European root that also gave Ancient Greek dasús. It measures how much matter is packed into a given volume, so it compares freely: lead is denser than aluminum. Solid says a thing is firm, while dense says how heavy it is for its size.

3. 3
   adjective

   Thick enough to be difficult to see through or pass through.

   A dense fog settled over the harbor, halting all the boats.

   The explorers hacked their way through dense jungle for days.

   Similarthick, solid

   Oppositethin

   Note

   This is the sense of forests, fog and jungle, where thickness becomes an obstacle. Ernest William White in 1881 describes slopes mantled by "still denser forests." Thick is its closest synonym, and both words make the same leap to the mind. W. B. Maxwell's The Mirror and the Lamp (1918) speaks of "dense stupidity," a dullness nothing gets through. That phrase is the bridge to the "slow-witted" meaning.

4. 4
   adjective

   Difficult to understand because of its complexity or tightly packed ideas.

   Her dense philosophical prose demanded several careful rereadings.

   The contract's dense legal language confused even the lawyers.

   Similarobscure, difficult, incomprehensible, impenetrable, mysterious

   Oppositeclear, simple, understandable, comprehensible

5. 5
   adjective

   Slow to understand things; lacking quickness of mind.

   Even after the third explanation, he stayed too dense to follow the plan.

   She called herself dense for missing such an obvious clue.

   Similarstupid, slow, dumb, thick, brainless

   Oppositesmart, intelligent, bright, quick

   Note

   Applied to a person, the word turns the "hard to follow" meaning around. Dense prose resists being understood, while a dense person fails to understand. It shares that picture of impenetrability with thick, its nearest synonym. It also stretches to machines: Cade Metz, writing in The New York Times in 2023, says systems like GPT-4 can "seem terribly dense."

6. 6
   adjective

   Allowing little light to pass through; nearly opaque.

   A dense layer of cloud kept the whole valley in shadow.

   Photographers fit a dense filter to cut the light reaching the lens.

   Similaropaque, cloudy, thick

   Oppositeclear, transparent, translucent

7. 7
   adjective

   Of a subset, having a closure equal to the whole space, so its points lie arbitrarily close to every point of the space.

   The rational numbers are dense in the real numbers.

   A set is dense when every open region around any point contains one of its members.

   Note

   In topology, a dense set leaves no gap anywhere: every open set of the surrounding space, however small, contains at least one of its points. Density here is always relative, because a set can be dense in one space and not in another. For that reason the word is followed by in, as in the rationals dense in the reals. It is also all or nothing, with no denser or densest.

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