In a survey of information theory and some of its implications, Warren Weaver has proposed a distinction between engineering (or channel) noise and semantic noise (1: 94–117). Ordinary Spanish usage reflects this distinction quite neatly. If A speaks to B and B responds with no entiendo, it means ‘I have not heard your words, because of interfering sound or lack of attention; please transmit the same message again’; if he responds with no comprendo, it means ‘I heard you all right, but what I heard doesn't make sense; please paraphrase or explain.’ Channel noise, thus, is the responsible factor when that which leaves a transmitter is not that which reaches the receiver; semantic noise is a discrepancy between the codes used by transmitter and receiver.