There's another piece of it which is tone. If you were standing at a checkout and the cashier wanted you to swipe your own card, he/she might say, "scan your c

There's another piece of it which is tone. If you were standing at a checkout and the cashier wanted you to swipe your own card, he/she might say, "scan your card please". But, while the words read as an imperative statement or command, you'd probably notice that the intonation is one akin to a question. For instance, the voice would rise at the end, as in inquiry.