What Is a Non-Continuous Function? Understanding Discontinuities in Math

What Is a Non-Continuous Function Understanding Discontinuities in Math

A non-continuous function is a function in mathematics that experiences breaks or interruptions in its graphical representation.

Imagine you’re drawing the graph of a function and suddenly you need to lift your pencil off the paper to continue the drawing elsewhere—this visual gap often signifies non-continuity.

Mathematically, non-continuity at a point occurs if at least one of three conditions is not met: the function must be defined at that point, both the left-hand and right-hand limits must exist and be equal, and these limits must equal the function’s actual value at that point.

Symbolically, if ( f ) is a function and ( a ) is a point in its domain, ( f ) is non-continuous at ( a ) if $\lim_{{x \to a^-}} f(x) \neq \lim_{{x \to a^+}} f(x)$ or if $\lim_{{x \to a}} f(x) \neq f(a) $, or if ( f(a) ) is not defined.

In my explorations of functions, I’ve learned that non-continuous functions often manifest as sudden jumps or holes in the graph, or they may approach a line that the function can never reach (known as a vertical asymptote).

Understanding these discontinuities is fundamental for anyone delving into calculus because it addresses the behavior of functions at specific points and how they interact with their limits—an undeniably exciting journey where each discontinuity tells a unique story.

Stick with me, and we’ll unearth the mysteries of discontinuous functions together!

Defining Non-Continuous Functions

In mathematics, when I discuss a function, I’m referring to a relation between a set of inputs (the domain) and a set of possible outputs (the range) with the property that each input is related to exactly one output.

A graph with a clear break or jump in the line, representing a non-continuous function

However, not all functions exhibit a smooth connection between their inputs and outputs. These are what we call discontinuous functions.

A discontinuous function includes at least one point at which the function is not continuous. To understand this better, it’s helpful to consider the concept of a limit.

Typically, for a function to be continuous at a certain point, the left-hand limit and the right-hand limit as we approach that point must be equal to each other and to the function’s value at that point.

Specifically, for a point ( c ) in the function’s domain, the following must be true for the function ( f(x) ) to be continuous at ( c ):

$$ \lim_{{x \to c^-}} f(x) = \lim_{{x \to c^+}} f(x) = f(c) $$


  • $\lim_{{x \to c^-}} f(x)$ is the left-hand limit.
  • $\lim_{{x \to c^+}} f(x) $ is the right-hand limit.
  • $f(c) $ is the value of the function at ( c ).

If any of these conditions are not met, a discontinuity exists. Discontinuities can occur when:

  • The limits do not exist.
  • The limits exist but are not equal.
  • The limits are equal, but the value of the function at that point is different.

I find it easier to identify discontinuities by looking at places where the function isn’t defined or where there’s a sudden jump or gap in the function’s graph.

These discontinuities are essential to understanding different mathematical behaviors and can deeply affect the outcomes of certain calculations, particularly in fields like physics and engineering.

Here’s a simple table to illustrate the types of discontinuities:

Type of DiscontinuityDescription
PointThe function is not defined at a point.
JumpA sudden change in function values.
InfiniteThe function approaches infinity.

Understanding discontinuous functions plays a crucial role in higher mathematics and can unveil many intriguing properties about the behavior of various mathematical models.

Characteristics and Types of Non-Continuous Functions

In my exploration of non-continuous functions, I’ve found that their defining characteristic is the inability to draw their graph without lifting your pen. Such functions are particularly interesting, as they often visually represent a sudden change in the value of a function.

There are three main types of discontinuities:

  1. Removable discontinuity: This can be visualized as a “hole” in the graph. The function approaches a certain value as ( x ) approaches from the left or right, but it’s not defined at that point. Mathematically speaking, if the limit of ( f(x) ) as ( x ) approaches ‘a’ from both sides is the same, yet ( f(a) ) is not defined or defined differently, it’s a removable discontinuity.

  2. Jump discontinuity: Here, the function makes a sudden “jump” at a point. If the limits of ( f(x) ) as ( x ) approaches ‘a’ from the left and right exist but are not equal, it’s a jump discontinuity.

  3. Essential discontinuity: This is where things get wilder. An essential discontinuity happens when the limit doesn’t exist as ( x ) approaches a point from either side. This could be due to wild swings in the function or behaviors like asymptotes.

Non-continuous functions aren’t usually differentiable at points of discontinuity since the derivative—which is the rate of change—does not exist where these sudden changes or jumps occur. To understand whether a function is continuous at a point, I look for these three criteria:

  • The function value at the point is defined.
  • The limit exists as ( x ) approaches the point from both sides.
  • The limit equals the actual function value at that point.

I also pay close attention to the behavior of functions on the real numbers. The absolute value function, for example, shows a removable discontinuity at ( x = 0 ).

Here’s a simple table summarizing the types:

Discontinuity TypeGraph featureLimit Behavior
RemovableHoleThe limit exists, but no value at the point
JumpSudden jumpLimits from left and right differ
EssentialErratic behaviorNo limit exists

Understanding these discontinuities is fundamental in the study of real-world phenomena where abrupt changes occur, such as in the stock market or natural events.


In exploring the characteristics of discontinuous functions, I’ve discovered a landscape rich with mathematical interest. A discontinuous function defies the smooth path one might anticipate in a continuous mathematical relation.

I find that the beauty of these functions lies in their complexity—each discontinuity tells a unique story. From jump discontinuities, where the function leaps from one value to another unexpectedly, to infinite discontinuities, where the function approaches infinity, the nuances are captivating.

Functions such as $f(x) = \frac{1}{x}$, which exhibits an infinite discontinuity at ( x = 0 ), illustrate how simple algebraic expressions can model complex real-world phenomena.

At points of discontinuity, the left and right limits of a function might exist, but they aren’t equal to each other or to the function’s value at that point. This is distinct from the graceful curve of a continuous function, where the function’s journey across its domain encounters no such interruptions.

Moreover, understanding discontinuity can be practical in fields like engineering and economics, where predicting behavior across diverse conditions is crucial.

My exploration has reinforced the idea that mathematical concepts, like discontinuous functions, provide essential insights into systems that are, by nature, not seamless.