# Does Wolfram Mathworld make a mistake describing a discrete probability distribution with a probability density function?

Usually a probability distribution over discrete variables is described using a probability mass function (PMF):

When working with continuous random variables, we describe probability distributions using a probability density function (PDF) rather than a probability mass function.

Deep Learning by Goodfellow, Bengio, and Courville

However, Wolfram Mathworld is using PDF to describe the probability distribution over discrete variables:

Is this a mistake? or it does not much matter?