Final answer:
A discontinuity in a function occurs when there is a point where the function is undefined, has a hole, or approaches different values from the left and right sides.
Step-by-step explanation:
A discontinuity in a function occurs when there is a point where the function is undefined, has a hole, or approaches different values from the left and right sides. In this case, the function provided has a discontinuity with 'dne' or 'does not exist' which means that there is a point where the function is undefined.