Oxford Dictionaries say by has the meaning of
6. indicating the period in which something happens: ‘this animal always hunts by night’
Then do we need to say, ‘Why does the sky glitter by night?’ And can’t we say, ‘Why does the sky glitter at night?’?
If we can use both, what’s the difference between the two?
Best Answer
The expression
by night
is typically used to contrast someone's nighttime activities to their daytime activities, especially when the nighttime activities are unusual or unexpected. You will see it very frequently in the constructionX by day, Y by night
. Some examples:On the other hand,
at night
is much less constrained as to the interpretation. The preferred thing to say will be that thesky glitters at night
, since this is the expected activity for a sky. To say that an animalhunts by night
uses theby night
expression because we normally think of day time as the time where animals should be most active, based on our own experience.Another useful note is that
by night
can almost always be replaced byat night
without altering the acceptability of the sentence, but not vice versa.