Enough is a common enough word in the English language that we never stop to think how strange it is.

Used as a qualifier of degree, or as Huddleston and Pullum express it, a sufficiency determinative, enough can modify verbs, nouns, adjectives and adverbs, and phrases. However it defies ‘normal’ word order.

When it qualifies a verb, adjective or adverb head, it behaves idiosyncratically by following that head:
big enough, *enough big
bravely enough, *enough bravely

The OED informs us that this is a recent change, and that in Old and Middle English enough often preceded adjective or adverb heads. The above behaviour is shared by the qualifiers galore and aplenty, although they may be becoming a bit archaic.

When it qualifies a noun, it most commonly precedes its head, as you would expect, but can sometimes follow it:
there is enough food and water to survive, ?there is food and water enough to survive
I have food enough, I have enough food

In its adjectival use, you can substitute the word sufficient for it, and in its adverbial use you can substitute the word sufficiently, but in both cases the substitute will precede its head, although it can follow a noun, particularly when it licenses a complement:
sufficiently big, *big sufficiently
sufficiently brave, *brave sufficiently
I have sufficient food, *I have food sufficient
sufficient food and water for ten men, food and water sufficient for ten men

When the head to enough has a complement, word order is again peculiar, for example (Huddleston and Pullum p 535):
he isn’t keen enough on the idea, ?he isn’t keen on the idea enough
he didn’t care enough about me, he didn’t care about me enough
*he doesn’t like enough the idea, he doesn’t like the idea enough

This can allow a range of possibilities (after Huddleston and Pullum p 535):
I’m not enough in control of things to go away
*I’m not in enough control of things to go away
?I’m not in control enough of things to go away
?I’m not in control of things enough to go away

These possibilities change in preference according to the frequency of use of the phrase, and dubious orders in this example may become preferential in other cases.

In case that is not enough, it can be used with of,
have you had enough of the soup
have you had enough soup

If anyone can simplify the above into a succinct set of rules, I would love to see them. Otherwise I think that enough is enough.

Once again these thoughts have been sparked by Peter Culicover and Ray Jackendoff’s Simpler Syntax (pp 26-7, Oxford UP, 2005). ‘Huddleston and Pullum’ refers of course to their Cambridge Grammar of the English Language (2002). The above follows the convention that an asterisk * precedes usage which is incorrect or deprecated, and a question mark ? signifies doubt or lower acceptability.