The two words ''cumulative'' and ''density'' contradict each other. Given a graph of the probability density function
<math display="block"> y={P}(x),</math>
<math>y</math> is the probability of finding just the particular value of the variable corresponding to <math>x</math> on the <math>x</math>-axis. It knows nothing about the probabilities to be found at other values of <math>x</math>, and therefore cannot be ''cumulative''. The cumulative distribution function, by contrast, is an accumulation of the probabilities of finding every value of <math>x</math> up to and including the current value indicated on the <math>x</math>-axis.
