existential quantifier

let $\text{[math]}$ be a relation and let $\text{[math]}$ be a variable, the expression $\text{[math]}$ means "there is an $\text{[math]}$ such that $\text{[math]}$ is true"

consider the sentence "there exists a human that is polite"
let a human be denoted by $\text{[math]}$ and a polite human by $\text{[math]}$
we can write this as $\text{[math]}$ or $\text{[math]}$

the existential quantifier is an abbreviation for there is a.
[cite:@jaynes_prob_2003 chapter 1.8.2 nitpicking]