This bookshop is a very nice bookshop with a small selection of linguistics books hidden at the bottom of a small set of shelves in the basement. But I wasn't there to peruse the books. It was lunchtime, I was having a break from seeing Ice Age things at the British Museum with my parents and we needed some lunch before going to see Pompeii and Herculaneum things. There's a very nice cafe in the bookshop, selling home-made sorts of food and a million types of tea. It's small though, and popular, so we had to wait for a table. The waitress suggested we wait in the bookshop and she'd come and get us when there was a free table.
I was telling my aunt about this when we met her later on, and I said:
They wait you in the bookshop.Wait is not normally used this way, but I liked it so I let it stand. Normally, wait doesn't have an object - that is, (roughly) something acted on by the verb. Sleep doesn't have an object (I slept) but catch does (I caught a rabbit), and eat either can or can't (I've eaten or I've eaten six Jaffa cakes). Wait is like sleep (I waited). What I said included an object: They wait you (we can ignore in the bookshop for now, because it's optional in the sentence).
Sometimes, we have verbs that change the number of objects they have (in this case from 0 to 1) because of some syntactic difference. This is different from eat, which either has a 'null' object meaning 'some unspecified kind of food' or just has two very closely related meanings.
Wait normally has a subject which is the person doing the waiting: if I say I waited, it's me who's done the waiting. With eat, that subject stays the same whether we add an object or not: I ate or I ate six Jaffa cakes, it's still me who ate something. But look at the sentence above: the subject is not the person who is waiting. When I said They wait you in the bookshop, it's not 'they' who are waiting, it's the object of the sentence, you (=us, in that case). So when I added the object, I also changed the role of the participants in the action.
What I meant by that utterance was, I suppose, They make you wait in the bookshop or They cause you to wait in the bookshop. I've turned it into what linguists, in an uncharacteristic show of naming things transparently, call a 'causative'. It's comparable to grow: I can say either I grew, and then it is me who became larger, or I can say I grew a plant or I grew the profits and then it is something else that I have caused to become larger.
It's also related to something called 'middle voice'. It's called that because it's in the middle between active and passive. If you think about a sentence like The cake cuts well, then the cake is grammatically the subject of an active verb, but the meaning is that the cake is the thing that is cut, and that's the meaning you'd get from a passive form: The cake has been cut. English doesn't do this loads, compared to some other languages, and that's not what's happening with wait above. It's just a similar phenomenon.