W dzień pracuję w biurze, a w nocy czytam książkę.

In the daytime I work in the office, and at night I read a book.

Breakdown of W dzień pracuję w biurze, a w nocy czytam książkę.

• w: in
• czytać: to read
• książka: the book
• pracować: to work

Questions & Answers about W dzień pracuję w biurze, a w nocy czytam książkę.

Why is it w dzień but w nocy? Why are they different?

Both mean during the day / at night, but they use different cases and slightly different structures:

• w dzień – literally in (the) day, but it works as an adverbial time phrase, similar to during the day.

  • dzień is in the accusative (same form as nominative for this noun).
  • This is a common, idiomatic way to talk about time.

• w nocy – literally in (the) night, also meaning at night.

  • noc in locative is nocy, so this is locative after w.
  • This one is more clearly a preposition + locative time expression.

In everyday speech, both patterns are normal and you just learn them as fixed expressions:

• w dzień – during the day
• w nocy – at night

Could you also say w dniu instead of w dzień?