A random variable is discrete if the values it can take on within an interval is finite.

PMF and CDF

The probability mass function (PMF) describes the probability distribution over a discrete random variable.

$p(x)=P(X=x)$

The cumulative distribution function (CDF) specifies the probability of an observation being equal to or less than a given value.

$F(x)=P(X\leq x)$

We usually have tables for these in the case of discrete random variables.

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