Dilation (or dilatation) refers to an enlargement or expansion in bulk or extent, the opposite of contraction. It derives from the Latin dilatare, "to spread wide".
In physiology:
- Pupillary dilation, dilation of the pupil of the eye
- Cervical dilation, the widening of the cervix in childbirth, miscarriage etc.
- Dilation and curettage, the opening of the cervix and surgical removal of the contents of the uterus
- Dilation and evacuation, the dilation of the cervix and evacuation of the contents of the uterus
- Vasodilation, the widening of luminal diameter in blood vessels
In mathematics:
- Dilation (affine geometry), an affine transformation
- Dilation (metric space), a function from a metric space into itself
- Dilation (operator theory), a dilation of an operator on a Hilbert space
- Dilation (morphology), an operation in mathematical morphology
- Scaling (geometry), including:
- Homogeneous dilation (homothety), the scalar multiplication operator on a vector space or affine space
- Inhomogeneous dilation, where scale factors may differ in different directions
In physics:
- Scale invariance, a feature of objects or laws that do not change if length scales (or energy scales) are multiplied by a common factor
- Time dilation, the observation that another's clock is ticking at a slower rate as measured by one's own clock
In metal working:
- Dimensional variation, the variation of physical dimensions in response to application or removal of heat
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