What does dilate mean?
"Dilate" is a verb meaning to make something wider, larger, or more open — or to become so. Its most familiar uses are medical and physiological: pupils dilate in low light, blood vessels dilate to increase blood flow, and the cervix dilates during childbirth. The word works both transitively, as when a drug dilates the arteries, and intransitively, as when the arteries simply dilate on their own. Beyond anatomy, "dilate" has a formal, somewhat literary sense of speaking or writing at excessive length, usually with the preposition "on" or "upon": a lecturer might dilate upon a favorite topic long past the point of usefulness. Derived forms such as "dilation," "dilator," and "dilated" appear constantly in medicine and science. Precise, versatile, and slightly clinical in flavor, "dilate" is a useful alternative to vaguer verbs like "expand" or "grow" whenever widening or opening is meant literally.
verbTo make or become wider, larger, or more open; to expand or stretch. In figurative use, to speak or write at length, elaborating on a subject.
- (of a part of the body, a passage, or an opening) to become or make wider, larger, or more open
- (literary or formal) to speak or write at great length; to elaborate on a topic (usually with 'on' or 'upon')
"The doctor administered drops to dilate her pupils before the eye examination."
"The medication caused her blood vessels to dilate, lowering her blood pressure."
"In his lecture, he tended to dilate upon the smallest historical details at the expense of the main argument."
Your pupils dilate not just in dim light but when you look at someone you find attractive — which is why the word comes up everywhere from optometry to poetry.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dilate
"Dilate" entered English in the late Middle Ages (attested by the 14th–15th centuries) from Latin "dilatare," formed from "dis-" (apart) plus "latus" (wide), literally meaning "to spread wide." It came into English partly through Old French "dilater." It shares this Latin root with "dilation" and, more distantly, with words built on the same "latus" stem such as "latitude" and "elate."
Related word forms
How dilate is actually used
"Dilate" is common in medical and scientific contexts (pupils, blood vessels, cervix) and is neutral in register. The figurative sense of speaking at length is somewhat formal or literary and typically takes the prepositions "on" or "upon." Both transitive ("the drug dilated the vessels") and intransitive ("the vessels dilated") uses are standard.
Easily confused with dilate
"Dilate" is the correct verb meaning to widen or expand; "dilatate" is not a standard English word and should not be used.