Variable

Type: notation

A variable is denoted using a letter,
\[
  a,\ b,\ c,\ \ldots
\]
and sometimes a Greek letter,
\[
  \alpha,\ \beta,\ \gamma,\ \ldots
\]
sometimes a capital letter,
\[
  A,\ B,\ C,\ \ldots
\]
and at other times some combination of the above.