Definition:Logical Formula

A logical formula (or, when the context is understood, just "formula") is a particular example of a statement form.

The plural of "formula" is usually given nowadays as "formulas", but the Classical plural "formulae" is frequently seen, particularly in older literature.

It is traditional, particularly in the field of mathematical logic, to use lowercase Greek letters to stand for general formulas (the usual ones being $$\phi, \psi$$ and $$\chi$$), but more modern treatments are starting to use ordinary lowercase letters of the English alphabet, usually $$p, q, r$$ etc.