An Etymological Dictionary of Astronomy and Astrophysics

i) If t₁, t₂, …, t_n are terms and P is a → predicate of arity n, then P(t₁, t₂, …, t_n) is an atomic wff.
ii) If t₁ and t₂ are terms, then (t₁ = t₂) is an atomic wff.

See also: → atomic; → wff.