Student or Learner
In the sentence 'I need to sleep 8 hours a night/day' my book says that the night is correct. Is the day then incorrect? (By the day I mean the whole day from the beginning of the previous night to the end of the current night)
Eight hours a day is commonly taken to mean a more-or-less continuous period of eight hours during each 24-hour day.
Eight hours sleep can be taken at any time - whether it's daylight outside or night-time.
Last edited by billmcd; 05-Jul-2011 at 14:50. Reason: typo
"a night" and "a day" are correct.
If you say, "I only sleep 2 hours a day" (but you sleep 6 hours each night), then you are being perverse, and not communicating in good faith.
The same applies if you say, without explaining, "I only sleep 2 hours every night" (if you sleep for 6 hours during the day).
If you want to specify that you are talking about "during the day" or "at night", etc. then you should use those terms, not "a day" or "a night".