adjective
1
BAD : In garage sales people get rid of their useless things.
GOOD : In garage sales people get rid of the things they don't use.
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If something is useless it is not useful: 'These scissors are useless - they don't even cut paper.' 'The report contains a lot of useless information.'
2
BAD : I don't like history because I think it's useless for me.
GOOD : I don't like history because I think it's of no use to me.
BAD : Why do we have to learn useless words?
GOOD : Why do we have to learn words that are of no use?
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If something does not help you to do what you want to do, it is (of) no use (to you) : 'I use my computer for writing and so a typewriter is of no use to me.' 'This map's no use - it doesn't show the minor roads.'
3
BAD : Staying in a big hotel would involve useless expense.
GOOD : Staying in a big hotel would involve unnecessary expense.
DUBIOUS : Without all this useless packaging, food would be cheaper.
GOOD : Without all this unnecessary packaging, food would be cheaper.
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If something is not necessary, it is unnecessary (NOT useless ): 'People who refuse to stop smoking are taking an unnecessary risk.' 'Sports that cause animals unnecessary suffering should be banned.'