What does "dense" mean?

1. (packed together) having parts that are very close together with little space between them. 2. (difficult to understand) containing a lot of information or difficult ideas that make it hard to read or follow. 3. (mathematical sets) used in math to describe a set where you can always find a point between any two other points. 4. (slow to understand) a slightly rude way to describe someone who does not understand things quickly.

dense

adj.

US //ˈdɛns// UK //dˈɛns// dense

1 packed together (adj.)
B2 Upper Intermediate

having parts that are very close together with little space between them.

characterized by a high degree of compactness or a high ratio of mass to volume.

Example

The hikers struggled to walk through the dense forest because the trees were so close together.

Example

The city's dense urban core presents significant challenges for planners attempting to integrate new green spaces without displacing existing residents.
- sparse
- thin
2 difficult to understand (adj.)
C1 Advanced Academic

containing a lot of information or difficult ideas that make it hard to read or follow.

intellectually challenging due to a high concentration of complex ideas or obscure language.

Example

I found the first chapter of the philosophy book very dense and had to read it twice.

Example

The report was so dense with technical jargon and statistical data that even the experts struggled to extract a clear policy recommendation.
- simple
- accessible

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3 mathematical sets (adj.)
C2 Proficiency Technical Math

used in math to describe a set where you can always find a point between any two other points.

describing a subset of a topological space whose closure is the space itself; every point in the space is a limit point of the set.

Example

The teacher explained that rational numbers are dense because there is always another fraction between any two.

Example

In any interval of the real line, the set of rational numbers is dense, ensuring that any real number can be approximated by a sequence of rationals.
4 slow to understand (adj.)
B2 Upper Intermediate Informal

a slightly rude way to describe someone who does not understand things quickly.

exhibiting a lack of mental agility or failing to grasp obvious points; slow-witted.

Example

I felt a bit dense when I realized the answer was right in front of me the whole time.

Example

He was usually quite sharp, but he seemed uncharacteristically dense when we tried to explain the new office procedures to him.

Origin

From Middle French dense, from Latin dēnsus, from Proto-Indo-European *dens- (“thick, dense”) (whence also Ancient Greek δασύς (dasús)).