Terminology of the Predicate Calculus
P, Q, R, P1, P2, ... , Q1, Q2, ..., R1, R2, ...
If P takes n arguments, we call P an n-ary predicate
P( term1, term2, . . . , termn)
f, g, h, f1, f2, . . . , g1, g2, . . . , h1, h2, . . .
a constant: e.g., a, b, c, a1, a2, . . . , b1, b2, . . . , c1, c2, . . .
a variable: e.g., x, y, z, x1, x2, . . . , y1, y2, . . . , z1, z2, . . .
an n-ary function symbol, followed by n terms in parentheses.
Examples of terms: x, a, f(x), g1(a, y), h(f(x), g(y, b))