verb
1
BAD : I ran downstairs to know what was happening.
GOOD : I ran downstairs to find out what was happening.
BAD : Two police officers visited him to know where he had been on the night of the murder.
GOOD : Two police officers visited him to find out where he had been on the night of the murder.
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find out = get information about something that you want to know: 'We need to find out why these cars have stopped selling.'
2
BAD : The best way to know the city is to visit it on foot.
GOOD : The best way to get to know the city is to visit it on foot.
BAD : When a woman goes out to work, she knows other people.
GOOD : When a woman goes out to work, she gets to know other people.
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know = be familiar with: 'I know Frankfurt very well.'
get to know = become familiar with: 'Once you get to know her, I'm sure you'll like her.' 'We got to know each other very well during the week we spent together.'
3
BAD : I got to know the south of London very deeply.
GOOD : I got to know the south of London very well.
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(get to) know sb/sth very well (NOT deeply ): 'I know Alex very well. We used to go to the same school.'
4
BAD : He knew well where he wanted to go.
GOOD : He knew exactly/precisely where he wanted to go.
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know sb/sth well = be fully familiar with: 'After living in Florence for two years, I know the city very well.' Compare: 'I'm completely against the idea, as you well know.'