thickness

thickness — noun

1. how closely packed or full of matter something is, so that it seems solid, crowd

1.nounB1
Definition

how closely packed or full of matter something is, so that it seems solid, crowded, or hard to see through — for example, a forest where trees grow very close, or fog so dense that it blocks your view.

Example

The thickness of the forest made it hard for sunlight to reach the ground.

collocation: thickness of + forest/fog/hair

Sora was surprised by the thickness of his cat's fur after the cold winter.

Common collocations
  • thickness of the forest
  • thickness of the fog
  • thickness of the hair
  • thickness of the fur
  • improve the thickness
  • increase the thickness
Synonyms
  • density

    more scientific; thickness describes how closely packed parts are, while density also involves weight per unit of space

  • compactness

    formal; focuses on the idea of parts being pressed tightly together

Antonyms
  • thinness

    the opposite quality — having few parts spread far apart

Grammar Patterns

the thickness of + noun

Usage Note

Uncountable only. Commonly paired with 'of' before the noun describing the dense material (e.g. the thickness of the fog, the thickness of the hair).

2. the distance from one surface of an object to the opposite surface, especially w

2.nounA2
Definition

the distance from one surface of an object to the opposite surface, especially when this is smaller than the object's length or width — for example, knowing that a wall is 20 centimetres from its front face to its back face.

Example

Cole measured the thickness of the wooden plank before cutting it.

collocation: measure/check the thickness

The old stone wall had a thickness of nearly two metres in some places.

Common collocations
  • measure the thickness
  • check the thickness
  • in thickness
  • a thickness of
  • wall thickness
  • board thickness
Synonyms
  • depth

    used for front-to-back or top-to-bottom measurements, but often overlaps with thickness in three-dimensional objects

  • gauge

    technical; used for metal sheets, wires, and screws instead of thickness

Grammar Patterns

a thickness of + number + unit

in thickness

Usage Note

Can be countable (different thicknesses for different measurements) or uncountable (general concept). When specifying a value, the pattern 'a thickness of [number]' is idiomatic.

Common Mistakes

The width of the board is 2 cm' (when you mean the smallest dimension).
The thickness of the board is 2 cm.
'width' measures from side to side; 'thickness' measures between the two largest surfaces.

3. a single sheet, coating, or level of a material that lies on top of something or

3.nounB1
Definition

a single sheet, coating, or level of a material that lies on top of something or between other materials — for example, putting several thicknesses of newspaper on a table before painting.

Example

The package was wrapped in several thicknesses of bubble wrap for protection.

countable: several thicknesses of

For extra warmth in winter, Linh wore two thicknesses of woollen socks.

Common collocations
  • single thickness
  • double thickness
  • several thicknesses
  • thickness of cardboard
  • thickness of glass
  • thickness of newspaper
Synonyms
  • layer

    more common in everyday language; 'thickness' emphasises the material's role as a covering

  • sheet

    used for flat, flexible materials like paper or metal; 'thickness' is broader

Grammar Patterns

a thickness of + noun

several thicknesses of + noun

Usage Note

Always countable. Frequently used in the plural (several thicknesses) or with modifiers like 'double', 'single', 'multiple' before 'thickness'.

Common Mistakes

A thickness of paper is on the floor' (vague).
Place a single thickness of paper on the floor.
Use 'single' or 'double' to make the meaning of 'layer' clear.

4. how slowly or easily a liquid pours, based on how strongly its parts resist move

4.nounB2
Definition

how slowly or easily a liquid pours, based on how strongly its parts resist movement — for example, the thickness of honey makes it pour much more slowly than water.

Example

Élise tested the thickness of the soup by watching how slowly it poured.

collocation: test/adjust the thickness of + liquid

In cold weather, engine oil has a greater thickness and flows more slowly.

Common collocations
  • thickness of the sauce
  • thickness of the honey
  • thickness of the oil
  • adjust the thickness
  • reduce the thickness
  • test the thickness
Synonyms
  • viscosity

    the formal scientific term; 'thickness' is the everyday word for the same idea

  • consistency

    broader term describing how firm or thick a substance feels; thickness focuses specifically on resistance to flow

Antonyms
  • thinness

    the quality of a liquid that pours easily, like water or milk

Grammar Patterns

the thickness of + liquid

adjust/reduce the thickness

Usage Note

Uncountable. In cooking, 'adjust the thickness' usually means add liquid (to reduce) or add flour/cornstarch (to increase). In engineering, 'viscosity' is the preferred technical term.

Common Mistakes

This sauce has a nice thickness' (when talking about food casually).
This sauce has a nice consistency.
In everyday conversation about food, 'consistency' sounds more natural than 'thickness.'

Word family

Synonym discussion

Sense: noun/2

All four words describe dimensions of objects, but they refer to different orientations. 'Thickness' is the smallest of the three dimensions — the distance between the two largest surfaces of an object. 'Width' measures from side to side (the second largest dimension), while 'depth' measures from front to back or top to bottom, depending on the object's orientation. 'Breadth' is a more formal synonym for 'width' and can also mean 'range' or 'scope' in figurative use. For example, a book might have a thickness of 3 cm, a width of 15 cm, and a depth (or height) of 22 cm. In building plans, you'd say 'the wall thickness is 20 cm' but 'the room width is 4 metres.'

depth ↗width ↗breadth

Common collocations

Nouns

Phrases

  • in thickness
  • of the same thickness

Prepositions

Etymology

Old EnglishMiddle EnglishEnglish

From Old English þicness, a combination of þicce ('thick', meaning 'dense, close together') and -nes (a suffix that turns adjectives into nouns, like -ness in modern English). The word has been used for over a thousand years. The measurement sense (the distance between opposite sides) appeared in the 1300s, and the meaning 'viscosity of a liquid' developed in the 1500s.