Most ordinary letters are accepted as variables. These may be subscripted or superscripted so long as it is understood that the variable formed is not semantically compound. For example "x_i" can be used for "x-inner" if no reference to a variable "i" is intended. For most mathematical purposes these variables are all that is needed. Symbolic logic expressions and some definitions require some special kinds of variables shown here:

\pvar - \tvar | Sentential Variables |

\ppvar -\ttvar | More Sentential Variables |

\pbar - \rbar | Unary Predicate Variables |

\pbarp - \rbarp | Binary Predicate Variables |

\pbarpp - \rbarpp | Ternary Predicate Variables |

\ubar - \wbar | Unary Function Symbol Variables |

\ubarp - \wbarp | Binary Function Symbol Variables |

\ubarpp - \wbarpp | Ternary Function Symbol Variables |

Examples:

(\pvar \Iff \qvar \c (\pvar \c \qvar))

(x = y \c \pbar x \Iff \pbar y)

(x \in \setof t \pbar t \Iff \pbar x \and x \in \U)