(i) He works (a) at night and sleeps (b) during the day.
(ii) Nocturnal animals sleep (c) by day and hunt (d) by night.
(source: OALD)

There’s a definite article in (b), while there're zero articles in the others. Why does (b) need one, while the others don't?

2 Answers 2


All those bolded examples are adverbial phrases, that is, a group of words acting together as an adverb.

As often is the case with phrases, it is easier to learn their meanings than reasoning about them. I think your question gives a good example where the article use cannot be deducted from the meaning of the phrase.

The collocation dictionary ozdic lists three meanings of day when used with a preposition. Note that the meaning depends on the preposition, and not on the article:

Preposition + day

  1. period of 24 hours

    • by the day: He's getting stronger by the day.
    • for a day: They stayed for a day.
    • in a day: We hope to finish the job in a day.
    • on the day of: On the day of his wedding he was very nervous.
  2. time between sunrise and sunset

    • by day: We travelled at night and rested by day.
    • during the day: He sleeps during the day
    • for the day: We went to the seaside for the day.
  3. particular period of time

    • in somebody's day: Things were very different in my grandfather's day.
    • of the day: the government of the day
  • 3
    +1 I'd also like to add this information. In Practical English Grammar (Michael Swan), 70.1 common expressions without articles, there is a good explanation: "in some common fixed expressions to do with place, time and movement, normally countable nouns are treated as uncountables, without articles." Mar 9, 2014 at 13:08

Very good question. Let me write what I think here. However, NSs would help us understand this in a better way.

He works at night and sleeps during the day.

I think the word day took the definite article because here, in this context, a person's routine and time period is already defined in the first clause - he works at night. Probably, the day is definite as it follows the night described in that sentence.

Nocturnal animals sleep by day and hunt by night.

Adding the will make it "...animals sleep by the day..." which would mean something different.

  • “During the day” seems not that simple. Because I find a sentence in Corpus of Con-temporary American English, “What kept you going during the day at night?”. And I also got these examples: “I teach during the day and do research at night”;" The crabs hide during the day and come out at night". So I get the feeling that ‘during the day’ alone has a definite article for denoting some meaning. There are variety of the examples in this Korean website.
    – Listenever
    Mar 9, 2014 at 6:05
  • @Listenever True but then if you carefully reread them all, you'll find some context of defining it as the day. As in I teach... you have night with it so the same context; in crab's example also, it's crabs' routine and thus the.
    – Maulik V
    Mar 9, 2014 at 7:11
  • 2
    I rather think that it’s the preposition during that license the definite article. For I can find dur-ing the night. Don’t you think the meaning of during forces the use of the?
    – Listenever
    Mar 9, 2014 at 7:50
  • 1
    @Listenever using the with during is quite common but then I already searched COCAE that showed several results on during a day. In my medical practice, I often come across something like Nausea during a day of long journey is expressed by the patient
    – Maulik V
    Mar 9, 2014 at 8:23
  • 2
    If your "already defined" conjecture was true, couldn't I reverse the sentence? He works at day and sleeps during the night. But that's not how I'd say it; instead, I'd say: He works during the day and sleeps at night. I think Nico's "depends on the preposition" idea seems more on the right track.
    – J.R.
    Mar 9, 2014 at 9:40

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