When we say that a function is defined at a point, it means that there is an actual value assigned to that specific input within the domain.
A property describing points where either the function is not defined or there are abrupt changes in the graph.
Vertical Asymptote: A vertical line that a graph approaches but never crosses, indicating a point where the function is undefined.
A type of discontinuity where a hole exists in the graph of a function, but it can be filled by redefining the value at that point.