An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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.

→ atomic; → wff.