Enough to shows sufficiency and has a positive meaning. Note that enough goes after the adjective or adverb it modifies.
- She is old enough to do things on her own.
- He is strong enough to lift that box.
- The boy was clever enough to solve the problem.
- They are rich enough to buy just about anything.
- He ran fast enough to catch the train.
- She worked hard enough to pass the test.
The phrase ‘not enough to’ shows insufficiency.
- She isn’t old enough to marry.
- He is not strong enough to lift that box.
- The boy was not clever enough to solve the problem.
- We aren’t rich enough to buy a car.
- He didn’t run fast enough to catch the train.
- She didn’t work hard enough to pass the test.
Enough goes after the adjective or adverb it modifies.
- She is old enough to have grandchildren. (NOT She is enough old to have grandchildren.)
- He is intelligent enough to solve that problem. (NOT He is enough intelligent to solve that problem.)
Enough can also modify nouns and then it goes before them.
- We have bought enough eggs. (NOT We have bought eggs enough.)
- She earns enough money to lead a comfortable life. (NOT She earns money enough to lead a comfortable life.)
Note the difference in the meaning when the position of enough changes.
- We haven’t got big enough tables. (= We need bigger tables. The tables that we have at the moment aren’t big enough.)
- We haven’t got enough big tables. (= Our tables are big enough, but we haven’t got enough of them. We need more big tables.)