Celine from France writes:
  I would like to know the differences in meaning and use of enough, sufficient and adequate.
Roger Woodham replies:
enough ?sufficient
Enough (where the second syllable is pronounced as in puff or stuff) and sufficient are very similar semantically, meaning as much as is needed:
I don't have enough time to finish reading this report before the meeting. But I have sufficient information to know what the outcome should be.
We have sufficient evidence to convict him for the crimes he has committed.
Adequate is also close in meaning to enough and sufficient. It suggests that something is good enough or large enough for a particular purpose:
This country will never maintain an adequate supply of trained teachers if so many leave the profession after four or five years.
This little car is perfectly adequate for any driving you need to do in town.
His computer skills were adequate for the type of work required of him.
inadequate ?insufficient
Note that the negative of sufficient and adequate can be formed with the prefix in-. For the negative of enough we have to use not:
The level of funding available for the training of teachers is inadequate.
I have insufficient resources to be able to deal effectively with this problem.
We don't have enough milk if everybody wants cappuccino.
enough as an adverb
Enough can also be used as an adverb to modify an adjective, an adverb or a verb. When it is used in this way, it comes after the adjective, adverb or verb:
In this climate it's not warm enough to go out without a jumper in the evening.
You've missed him, I'm afraid. You didn't get up early enough.
I didn't work hard enough so I was unsuccessful in the exam.
I didn't revise enough so I didn't pass the exam.
Modifying adverbs, of course, are normally placed before the adjectives or adverbs that they modify, so if we want to use the less common sufficiently in these examples instead of enough, they will look like this:
In this climate it's not sufficiently warm to go out without a jumper at night.
You've missed him, I'm afraid. You didn't get up sufficiently early.
I didn't work sufficiently hard so I was unsuccessful in the exam.
I didn't revise sufficiently so I didn't pass the exam.
enough as a pronoun
Enough can also be used alone without a noun when the meaning is clear:
I've only saved up ?50. Will that be enough for this type of holiday?
Some more dressing on your salad? ~ Oh no, I have quite enough, thanks.
Enough of + determiner / pronoun
Before determiners (this, the, etc) and pronouns we use enough of:
I've had quite enough of this fruit salad, thanks. It's a bit too sweet for my liking.
I didn't read it all, but I read enough of the report to get the main idea.
I answered all the questions, but I didn't get enough of them right to pass the driving test.
As you can see, Celine, enough is commonly used in a wider variety of contexts than sufficient or adequate. I haven't mentioned all of them, but that is enough for today!
Enough is enough!
as we say when we want to indicate that we wish to bring something to an end.