noun
1
DUBIOUS : The length of the tunnel is about two miles.
GOOD : The tunnel is about two miles long.
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When you mention how long something is, a phrase ending with long usually sounds more natural than the length ... is , especially in informal styles: 'The garden is almost seventy feet long.'
2
DUBIOUS : The length of the film is one and a half hours.
GOOD : The film lasts one and half hours.
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last = take (a stated length of time) from start to finish: 'Each lesson lasts fifty minutes.' 'This afternoon's exciting match on centre court lasted exactly two hours and twelve minutes.'