What does dilatation mean?
Dilatation is a noun denoting the act of widening something or the state of being widened, from the Latin dilatare, 'to spread out.' Though it appears in general usage, it is most at home in medical and scientific language, where it describes the enlargement of hollow structures: the dilatation of blood vessels such as the aorta, of the pupil in response to darkness, of the cervix during labor, or of segments of the digestive tract. Such widening may be entirely normal, as with pupillary dilatation in dim light, or pathological, as when an aneurysm represents dangerous dilatation of an artery. Physicians also use the word for deliberately induced widening, such as balloon dilatation of a narrowed artery or esophagus. A close synonym is 'dilation,' which dominates everyday English; 'dilatation' survives chiefly because it sounds more precise and clinical. For readers, encountering dilatation almost always signals a technical discussion of anatomy, physiology, or pathology rather than casual speech.
The act or process of widening or being widened; the state of being expanded.
"Cervical dilatation is carefully monitored during the active phase of labor."
In clinical writing, often paired with the affected structure, as in 'aortic dilatation' or 'bronchial dilatation'.
(Medicine) Abnormal, physiological, or therapeutic enlargement of a hollow organ, vessel, or body passage.
"Balloon dilatation was performed to relieve the stricture in the patient's esophagus."
The plural is rare and typically appears only in medical literature describing multiple instances or sites of widening, e.g. multiple aneurysmal dilatations along an artery.
"The angiogram revealed several small fusiform dilatations along the mesenteric vessels."
Your pupils perform dilatation every time you walk into a dark room — the same word cardiologists use to describe a dangerously stretched aorta.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dilatation
Dilatation derives from the Latin verb dilatare, meaning 'to enlarge, spread out, or extend', formed from dis- ('apart') plus latus ('wide'). It entered English via Old French in the late Middle Ages, with the related verb 'dilate' attested slightly earlier in the sense 'to speak at length' before narrowing to its physical meaning. Cognates include French dilatation and Spanish dilatación, all tracing back to the same Latin root that also gave English words like 'latitude'.
Related word forms
How dilatation is actually used
Formal in register; overwhelmingly found in medical, scientific, and technical writing. In general prose, 'dilation' is far more common, though some style guides in medicine reserve 'dilatation' for anatomical structures and use 'dilation' more broadly. Both forms are accepted in British and American English.
Easily confused with dilatation
Both mean the act of widening, but 'dilation' is the more common everyday form, while 'dilatation' is preferred in formal medical and technical contexts (e.g. 'aortic dilatation'); they share the same meaning but differ in register.