Dilation is expansion, usually of an opening such as the pupil. When that happens, your eyes look black and the light comes streaming in. Grab your sunglasses!

The word dilation is the noun form of dilate, "to make wider.” Dilation often refers to what happens when a woman goes into labor, and her cervix dilates to let the baby through. Dilation is also used for writing or speech that expands on a topic. Here’s a dilation: funny thing is that the -ate ending of dilate is not a suffix but part of the word, so it should really be dilatation, but no one says it that way.

Definitions of dilation
  1. noun
    the act of expanding an aperture
    “the dilation of the pupil of the eye”
    synonyms: dilatation
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    dilation of blood vessels (especially the arteries)
    reflex pupillary dilation as a muscle pulls the iris outward; occurs in response to a decrease in light or certain drugs
    type of:
    enlargement, expansion
    the act of increasing (something) in size or volume or quantity or scope
  2. noun
    (mathematics) a transformation that changes the size of a figure but not its shape
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    type of:
    (mathematics) a function that changes the position or direction of the axes of a coordinate system
  3. noun
    a lengthy discussion (spoken or written) on a particular topic
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    type of:
    discourse, discussion, treatment
    an extended communication (often interactive) dealing with some particular topic
Word Family

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