dilate

American  

[dahy-leyt, dih-, dahy-leyt] / daɪˈleɪt, dɪ-, ˈdaɪ leɪt /

verb (used with object)

• dilates,
  present (3rd person singular)
• dilated,
  past participle,  past
• dilating
  present participle

1. to make wider or larger; cause to expand.

2. Archaic. to describe or develop at length.

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verb (used without object)

• dilates,
  present (3rd person singular)
• dilated,
  past participle,  past
• dilating
  present participle

1. to spread out; expand.

2. to speak or write at length; expatiate (often followed by on orupon ).

dilate British  

/ ˌdaɪləˈteɪʃən, ˌdɪ-, daɪˈleɪt, dɪ-, daɪˈleɪtɪv, dɪ- /

verb

1. to expand or cause to expand; make or become wider or larger

   the pupil of the eye dilates in the dark

2. (intr; often foll by on or upon) to speak or write at length; expand or enlarge

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Synonym Usage

See expand.

Other Word Forms

Derived Forms

• dilatability
  noun
• dilation
  noun
• nondilatability
  noun
• overdilate
  verb
• redilate
  verb
• dilatable
  adjective
• dilatational
  adjective
• dilative
  adjective
• nondilatable
  adjective
• self-dilated
  adjective
• subdilated
  adjective
• undilatable
  adjective
• undilated
  adjective
• undilating
  adjective

Inflected Forms

Participles

• dilating
  present
• dilated
  past

Conjugated Forms

Present

• dilate
  simple
• dilates
  simple
• have dilated
  perfect
• has dilated
  perfect
• am dilating
  progressive
• are dilating
  progressive
• is dilating
  progressive
• have been dilating
  perfect progressive
• has been dilating
  perfect progressive

Past

• dilated
  simple
• had dilated
  perfect
• was dilating
  progressive
• were dilating
  progressive
• had been dilating
  perfect progressive

Future

• will dilate
  simple
• will have dilated
  perfect
• will be dilating
  progressive
• will have been dilating
  perfect progressive

Etymology

Origin of dilate

First recorded in 1350–1400; Middle English dilaten, from Middle French dilater, “to comment at length, enlarge,” from Latin dīlātāre “to spread out, widen,” equivalent to dī- di- ² + lāt(us) “wide” + -āre infinitive suffix

Explanation

To dilate something is to make it wider. When the light fades, the pupil of your eye will dilate, meaning it looks bigger. The verb dilate comes from the Latin word dilatare, which means “enlarge” or “spread out.” When something stretches, expands, or becomes wider, it is said to dilate. Usually the word dilate is used when the opening of something circular becomes larger, but every so often you might hear someone refer to the need to dilate someone's understanding of quantum physics, global warming, livestock breeding, or any other topic.

Example Sentences

See Examples For:

dilate dilates dilated dilating

Atropine eye drops are typically used to dilate the pupil before eye exams.

From The Wall Street Journal ● Dec. 28, 2025

As a result, blood flow to that area increases dramatically as blood vessels dilate, causing pain and swelling.

From National Geographic ● Feb. 21, 2024

Although it is not an ordinary high blood pressure medicine, it can dilate blood vessels.

From Seattle Times ● Nov. 22, 2023

For example, the pupil tends to dilate during complex cognitive tasks or in response to unexpected stimuli.

From Science Daily ● Oct. 24, 2023

It made her skin flush and her eyes dilate, and some part of her marveled at the focus of the energy that ran through her.

From "Huntress" by Malinda Lo

It's a different sort of time and it moves, it dilates.

From Salon ● Feb. 6, 2024

Their study, published Dec. 5 in the journal Cell, focuses on nitric oxide, a compound that dilates blood vessels, improves memory, fights infection and stimulates the release of hormones, among other functions.

From Science Daily ● Dec. 8, 2023

Adenosine is a by-product of energy metabolism, but it also acts as an inhibitory neurotransmitter—a chemical messenger that affects brain cells and dilates blood vessels.

From Scientific American ● Oct. 25, 2023

The drug also dilates the cervix and blocks the effects of progesterone, which is needed to sustain a pregnancy.

From Washington Post ● Aug. 8, 2022

At the edge of the rectangle, a thin slit of light dilates wider.

From "100 Sideways Miles" by Andrew Smith

And if the aorta is dilated a certain amount, patients often undergo an elective surgery to fix it.

From MarketWatch ● Jul. 13, 2026

Rhys Llewellyn, 40, was diagnosed with dilated cardiomyopathy as a baby after struggling with breathing and putting on weight.

From BBC ● Jun. 20, 2026

In a dark room, a doctor pointed to an hourglass shape glowing on the ultrasound screen: There was her amniotic sac, funneling into her dilated cervix, and there was their tiny daughter’s foot, dipping out.

From Salon ● May 27, 2026

About 35 minutes in, Lamphere’s vitals started spiking; her heart rate quickened, she grew hot, her pupils dilated, she began grinding her teeth.

From Slate ● Jan. 30, 2026

They had bloody noses, and their eyes were half-open, glassy, and brilliant red, with dilated pupils.

From "The Hot Zone" by Richard Preston

Scholars and intellectuals dilating in their little books: None of that matters anymore.

From The Wall Street Journal ● Jan. 15, 2026

Erectile dysfunction drugs, which work by dilating blood vessels to allow more blood to flow through, were first developed to treat high blood pressure.

From Science Daily ● Feb. 7, 2024

The exhaustive format played to President Macron's strengths: his mastery of detail and obvious delight in dilating on every conceivable subject.

From BBC ● Jan. 17, 2024

Some also have trouble with the lining of their small blood vessels not dilating and constricting properly to move blood through, she added.

From Seattle Times ● Aug. 9, 2023

Kaede’s eyes were light brown; Taisin saw her pupils dilating as they looked at each other, dusk spinning out around them, cloaking them in shadow.

From "Huntress" by Malinda Lo

Related Words

• expound