Binary connectives, like &, v, -> and <->, combine with two formulas as in (i), the unary connective Neg combines with one formula as in (ii).
Phi & Psi (and) Phi v Psi (or) Phi -> Psi (if ... then ...) Phi <-> Psi (... if and only if ...)
Neg Phi (not)
The truth-value of the complex formula is always a function (a truth-function) of the truth-values of the formulas Phi and Psi, which can be represented in a truth table.
Gamut, L.T.F. 1991. Logic, language, and meaning. Chicago: University of Chicago Press.