Modal Verbs

In primary school, you were always told 'a verb is a doing word', even in secondary education, you may have never been taught differently because differentiation with verbs isn't that important at GCSE level. When you get into higher-education, and if you're looking to take a course in English, the difference in verbs gets serious, you cannot just say 'it's a doing word', you must be able to categorise a verb to a certain 'type'. Being able to notice if more epistemic/deontic verbs are being used in a text, it's A-level analysis, the highest level you get.

Used in more informal texts. Epistemic verbs normally have a degree of possibility in them. In most epistemic verbs, the speaker will be asking a question or wondering on "what to do", in any case, epistemic verbs will not be used in a commanding way or they would be deontic.

Used in more formal texts. Deontic verbs will be used in cases where the speaker is of a higher status then the listener (e.g. a Commander in the Army briefing his troops). Deontic verbs are usually not found in informal texts, and if they are, you can normally link the deontic verb with an epistemic (e.g. you ought to tune in to Capital 102.3 at 5pm, for the big music top 40!).

Modal Verbs: these are all the modal verbs I can think of -

• Can - Normally epistemic, unless the speaker is detailing a higher command that he "can do this". Put into a sentence "Yes, I can work nine till 5", the speaker is obligating himself, and there is no sense of possibility within the text.
• May - Probably the most epistemic word out of all them. May constitutes a degree of possibility in near to every sentence found in. If I put it into a sentence "I may require extra assistance", even though the speaker is obligating he'll need more help, there's a notion of possibility in the sentence, allowing the listener to believe he may not need help.
• Ought - A deontic verb, ought normally pushes to deontic in all contexts. When ought is used, it pursues a degree that the listener will do the command.
• Might - Like may, very epistemic. Hardly used in deontic contexts, due to it being a verb which has possibility in it. A bad case of using this a deontic text is "You could work nine till five", it just doesn't go with what the company is wanting you to do. It wouldn't be a case of "you could", more, you should, or you'll not be working there much longer.
• Shall - In the middle of epistemic & deontic. Shall is a complicated verb, in some contexts, it's deontic because it gives the impression they're going to do the task. In other contexts, shall may be referred to as something they "may" do. Example of this can be "I shall go to the premier tonight", yes, he's telling the listener he shall, but he may not, in theory, he may only be saying this as his friend has asked him. Shall still strikes a small sense of possibility.
• Could - Another epistemic verb. Could doesn't range from epistemic to deontic, it stays at epistemic. Like may, it's something you can only used in informal texts and is not a command word.
• Will -Like shall, this is borderline deontic/epistemic. In some contexts it can be seen as epistemic, although it's more deontic.
• Should - Another deontic verb. Should is a verb that doesn't have possibility in, the verb is normally used in statements where the listener is commanded to do something, it's just a light command. It can be seen as a informal deontic verb in some contexts.
• Must - The most deontic verb of all them. Must registers as the word most leaders use to their listeners. "We must pull together to get through this recession" - "I must run to the shops, we're out of bread" - "We must be careful, these rocks are slippy". In all cases, it doesn't question the listener, it commands the listener.
• Would - Another epistemic verb. Used in contexts where the speaker is too lazy, examples of this "I would do that, but I'm too tired" - "I would come out, but I've got other things to do" - "If I could, I would" (two epistemic's!)

If you can remember what epistemic and deontic verbs are, you can categorise all the verbs I've just said into both. It really just depends which context the verb is in.