dilation

Etymology

It is formed from English dilate + -ion,^[2][3][4][5] irregularly, as if dilate ended in the Latin verbal suffix -ate and took -ation like other verbs in -ate;^[2][6][7] in dilate the -ate belongs to the stem.^[7] The regular form, dilatation, is older, from about 1400.^[7][2] The verb dilate is from French dilater and directly from Latin dīlātō (“to make wider, enlarge”),^[7][2] from dis- (“apart”) and lātus (“broad, wide”).^[7][2]

Earliest recorded meaning

Widening or expansion, the same as dilatation: first recorded in Florio's Italian–English dictionary A Worlde of Wordes (1598).^[2][8] Etymonline and Dictionary.com likewise date it to the 1590s,^[7][4] while Merriam-Webster and the Shorter Oxford date it to the 15th century.^[3][9][6]

Semantic evolution

The word took over the senses of dilatation: physical widening, the spreading of immaterial things (in Donne, before 1631, a sense now obsolete), and the treating of a subject at length in speech or writing (1623, in Cockeram's dictionary).^[2][8] The last sense is still recorded by the American Heritage Dictionary.^[10] In modern use it is above all a medical term, for the natural or artificial widening of a hollow organ or opening, such as the pupil or the cervix;^[9][10][11] in mathematics it is a transformation that gives a figure similar to the original but of a different size.^[12]

Timeline

• 1598 – widening, expansion.^[2][8]
• 1623 – the treating of a subject at length.^[2][8]
• before 1631 – the spreading of immaterial things (now obsolete).^[2][8]

Meanings

Noun

1. The act of dilating or the state of being dilated; expansion, dilatation.^[9][10][4]
2. (medicine) The stretching or enlarging of an organ, opening or hollow structure of the body, naturally or by surgery: dilation of the pupils in dim light.^[9][10][11]
3. A lengthy spoken or written treatment of a topic.^[10][2]
4. (mathematics) A transformation that enlarges or reduces a figure without changing its shape.^[12]

Word family

• overdilation
• vasodilation
• dilation and curettage
• time dilation

Related words

• dilate
• dilatation
• dilatory
• latitude

Usage notes

A different noun dilation, meaning delay or postponement, was used from 1430 (in Lydgate) to 1665;^[2][6][8] it was borrowed from Old French dilacion, from Latin dīlātiō, a noun of action from differō (“to put off, defer”), the source of dilatory.^[2][6]

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
4. ^ a b c Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
5. ^ Gove, Philip Babcock, ed. (1961), Webster's Third New International Dictionary of the English Language, Unabridged, Springfield, Mass.: G. & C. Merriam
6. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
8. ^ a b c d e f Kay, Christian; Roberts, Jane; Samuels, Michael; Wotherspoon, Irené, eds. (2009), Historical Thesaurus of the Oxford English Dictionary, Oxford: Oxford University Press; online edition (2024)
9. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
10. ^ a b c d e The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
11. ^ a b Stedman's Medical Dictionary, Baltimore: Lippincott Williams & Wilkins
12. ^ a b The Chambers Dictionary (2008), 11th ed., Edinburgh: Chambers Harrap