" There is exactly one plane through three non-collinear instances of these objects.
The general branch of topology dealing with continuity, compactness, and connectedness is named after sets and these objects. A cusp is a variant of the "singular" type of these objects. If a function maps one of these objects to itself, then that object is called "fixed." These objects' relative distances from a circle are expressed as their namesake power. An open set does not contain any of these objects that are on its (*)  boundary. The second derivative test can often identify stationary instances of these objects, which can be a minimum, maximum, or one of these objects "of inflection." There is exactly one plane through three non-collinear instances of these objects. For 10 points, name this basic unit of Euclidean geometry, an infinite number of which are in a line.
The general branch of topology dealing with continuity, compactness, and connectedness is named after sets and these objects.
point s [accept  point-set  topology]