verb
1
BAD : I am concentrated on both speaking and writing.
GOOD : I am concentrating on both speaking and writing.
BAD : A bus driver has to be concentrated and should not speak to the passengers.
GOOD : A bus driver has to concentrate and should not speak to the passengers.
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concentrate ( on sth ) NOT be concentrated : 'How can children concentrate on their homework when they have one eye on the television?'
Compare: 'The juice is then concentrated by a process of evaporation.'
2
BAD : The teaching tends to concentrate in grammar.
GOOD : The teaching tends to concentrate on grammar.
BAD : I try to concentrate in one subject at a time.
GOOD : I try to concentrate on one subject at a time.
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concentrate on sth (NOT in ): 'She gave up teaching so that she could concentrate on research.'
3
BAD : I couldn't concentrate myself as there was someone talking.
GOOD : I couldn't concentrate as there was someone talking.