existential quantifier: a logical quantifier of a proposition that asserts the existence of at least one thing for which the proposition is true
quantifier: (logic) a word (such as `some' or `all' or `no') that binds the variables in a logical proposition
linguistic performance: (linguistics) a speaker's actual use of language in real situations; what the speaker actually says, including grammatical errors and other non-linguistic features such as hesitations and other disfluencies (contrasted with linguistic competence)