 Fârâbî assumes that Greek (like Arabic) distinguishes syntactically between tensed and tenseless sentences, and that (unlike Arabic) it expresses the copula in both kinds of sentences. Because, according to Aristotle’s definition of “verb” in On Interpretation 3, a verb must “consignify a time”, the tenseless copula cannot be a verb. Nor can it be a noun: if to predicate one noun of another we must insert a third noun between them, there will be an infinite regress of copulas. So the tenseless copula estin (or astîn), in Greek as Fârâbî reconstructs it, must be a particle, although there will also be tensed copulas which are verbs paronymously derived from this particle. He also thinks that the same particle can function, not only in 2-place contexts, i.e., in tenseless predicative statements “X is Y”, but also in 1-place contexts, i.e., in tenseless statements of existence “X is”: and he assumes that this is the word that Aristotle is discussing in the chapter on the meanings of being, Metaphysics V,7.