capillary

capillary — noun

1. the smallest type of blood vessel in the body, connecting the arteries to the ve

1.nounB2
Definition

the smallest type of blood vessel in the body, connecting the arteries to the veins, with walls thin enough for oxygen and nutrients to pass into nearby cells.

Example

When you exercise, the capillaries in your muscles widen to let more blood flow through.

capillary + singular generic article

Dr. Okafor studied how damaged capillaries affect healing after a skin injury.

capillary + plural for body part context

Common collocations
  • blood capillaries
  • capillary network
  • capillary wall
  • capillary action
  • tiny capillaries
  • damaged capillaries
  • broken capillaries
Synonyms
  • microvessel

    more technical; used mainly in medical research writing

Grammar Patterns

capillary + verb

capillary + of + body part

Usage Note

This sense almost always appears in the plural (capillaries) because a single capillary rarely works alone — they form networks throughout the body.

Common Mistakes

Blood flows through capilaries.
Blood flows through capillaries.
The spelling has two 'p's and two 'l's: cap-ill-ar-ies.
The capillary carries blood from the heart.
Capillaries connect arteries to veins, not directly to the heart.
Capillaries are tiny branching vessels, not the main blood pipes from the heart.

capillary — adjective

Word family

  • capillarity
    nounC2

Synonym discussion

Sense: noun/1

A capillary is the smallest type of blood vessel in the body — so thin that red blood cells pass through it one at a time. 'Blood vessel' is the general term for any tube that carries blood (capillaries, arteries, and veins all qualify). An 'artery' carries blood away from the heart, has thick, muscular walls to handle high pressure, and is much larger than a capillary. A 'vein' carries blood back toward the heart, has thinner walls than an artery, and contains valves to prevent backflow. Capillaries are different from both: they form branching networks (capillary beds) where oxygen and nutrients actually leave the blood and enter the body's cells. For example: 'The doctor explained that a bruise forms when small capillaries break under the skin' — here 'capillaries' is the right word because the break is in tiny, fragile vessels, not in a large artery or vein.

capillary ↗blood vesselarteryvein ↗

Common collocations

Nouns

Phrases

  • capillary action
  • capillary network
  • capillary bed
  • broken capillaries
  • capillary pressure

Etymology

LatinEnglish

From Latin 'capillaris' meaning 'of or like hair', from 'capillus' meaning 'hair of the head'. The word was first used in the 1600s by biologists who noticed that the tiniest blood vessels in the body branched like hairs — and were just as thin. The adjective sense followed naturally: anything hair-thin or with a hair-thin opening became 'capillary'.