Dilation

Dilation is the act of expanding something. This term is usually used by eye doctors in the context of "dilating the pupils".

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In mathematics, a dilation is a function f from a metric space into itself that satisfies the identity

<math>d(f(x),f(y))=rd(x,y)<math>

where d(x,y) is the distance from x to y and r is some real number. A dilation of a Euclidean space is called a similarity.