Definition 6.3.3: Classification of Discontinuities
Suppose f is a function with domain D and
c
D
is a point of discontinuity of f.

- if
f(x) exists, then c is called removable discontinuity.
- if
f(x) does not exist, but both
f(x) and
f(x) exit, then f is called a discontinuity of the first kind, or jump discontinuity
- if either
f(x) or
f(x) does not exist, then c is called a discontinuity of the second kind, or essential discontinuity.