different between tacnode vs acnode

English

Latin tactus + English node

tacnode (plural tacnodes)

(geometry) A point of a curve where two or more osculating circles to the curve at that point are tangent, so that two branches of the curve have ordinary tangency at the double point.

Latin acus + nodus

acnode (plural acnodes)

(geometry) An isolated point not upon a curve, but whose coordinates satisfy the equation of the curve so that it is considered as belonging to the curve.

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