Meaning of LONG in English

LONG

I

adverb

BAD : I'll go with you as long as I won't have to sing.

GOOD : I'll go with you as long as I don't have to sing.

II

adjective

BAD : I am afraid it will take long to improve my English.

GOOD : I am afraid it will take a long time to improve my English.

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Use take long in questions and negative sentences: 'How long does it take to get to London by train?' 'It doesn't take very long.'

Use take a long time in affirmative sentences: 'It might take a long time to sort out the problem.'

Longman Common Errors English vocabulary.      Английский словарь распространенных ошибок Longman.