The oldest, shortest words— "yes" and "no"— are those which require the most thought.

est etenim comis brevitas. sic fama renatum | Pythagoram docuisse refert : cum multa loquaces | ambiguis sererent verbis, contra omnia solum | “est” respondebat vel “non”. o certa loquendi | regula! | (“For brevity is indeed polite. Thus, legend has it that Pythagoras, once reborn, taught the following: when babblers would string together mouthfuls with indecisive words, to everything he used to respond simply ‘Yes’ or ‘No’. O what a steadfast rule of speech!”) link