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# Tacnode

In geometry, a tacnode is a species of singular point of a curve. It is defined as a point where two (or more) osculating circles to the curve at that point are tangent.

For example, the Links curve with equation $\left(x^2+y^2-3x\right)^2 -4x^2\left(2-x\right) = 0$ has a tacnode at the origin.