I don't fly but I would guess it would be the same as computer programming. The pilots probably learn a set of commands that ATC will give them, these commands will be a standard set around the world, so it won't necessarily be "English" that is spoken on the radio, more an international code language.
When I did amateur radio we had various Q-codes and number codes like 73's, 88's, QTH, QRZ - all these meant the same no matter which country you were from and that way we could speak to each other regardless of language, and it was it's own language known mainly by the amateur radio community. I would guess that pilots have the same thing - for example in amateur radio the following would mean
2: QTH Berlin"
1: Where are you?
2: I'm in Berlin
I don't know whether pilots use Q codes but I guess they must have something similar to this
Also there has been other things that have used these radio codes - for example the messenger service ICQ was named because the code for calling for a response on radio is to CQ ("Seek You") someone - "CQ, CQ, this is GW0AAA /MM calling CQ" means that someone with the call sign of G0AAA is in Wales on a boat of some sort and they're calling out to anyone who may be interested in having a chat (also the callsign gives you additional information about the person your speaking to - I assume pilots have similar things a callsign that starts G or M indicates that the persons amateur radio licence is from the UK, the second letter is used to indicate which part of the UK the person is calling from - England doesn't have a secondary letter but Wales has W, Scotland is M, NI is I, IoM (D), Guernsey (U) and Jersey (J) are also included even though technically they're separate from the UK with their own government) and the end bit also tells the person even more information - for example /M = the person is mobile, /T they're in a temporary location, /MM is maritime mobile, etc - but with all that extra information you don't really need to know English to work out roughly where that person is.
And finally with modern translation services and computer systems I would also guess that anything that comes through the radio now on a plane would also probably be sent to a screen on the dashboard, which has the ability to translate - just a guess but can't see why this isn't incorporated into planes (it is on Microsoft Flight Sim and that's supposed to be "As Real As It Gets!" - although I have heard that XPlane is much more real!) - and it wouldn't need to be a very big dictionary of words either for translation because there would only be a select number of phrases you'd need, your not really going to sit there and have a full on conversation with ATC are you - both them and you want to keep communication short and to the point because other people also need to use the radio comms.