adjective
1
BAD : Every alive creature in the sea is affected by pollution.
GOOD : Every living creature in the sea is affected by pollution.
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alive = not dead: 'He was very seriously ill and is lucky to be alive.'
living = (1) alive now: 'He has no living relatives.' (2) used to refer to all creatures and things that live and die: 'Yeast is a living organism and too much heat or cold can kill it.' 'The ants will eat any living thing that comes into their path.'
2
BAD : Our teacher, Mr Collins, is very alive.
GOOD : Our teacher, Mr Collins, is very lively.
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lively = full of energy: 'The Yorkshire Terrier is a lively breed of dog.'
3
BAD : My reason for being alive had disappeared.
GOOD : My reason for living had disappeared.
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When you mean 'continue to be alive', use the verb live : 'Her grandmother lived to a great age.' 'The baby was four months premature and was not expected to live.'