Рабочий день был долгим.

to be

Breakdown of Рабочий день был долгим.

• долгий: long
• рабочий день: the workday

Questions & Answers about Рабочий день был долгим.

Why is долгим used instead of долгий?

Долгим is the instrumental case form of the adjective долгий (masculine, singular). In this sentence it’s used as a predicate after the verb был (to be in the past tense):

• долгий – nominative (dictionary form)
• долгим – instrumental (masculine singular)

Russian often uses the instrumental case for the complement after быть in the past or future. So:

• Рабочий день был долгим. – The workday was long.

You can also hear Рабочий день был долгий. (nominative), which is grammatically possible. The difference is subtle: instrumental often sounds a bit more like “turned out to be / felt / was characterized as long,” while nominative is a bit more neutral or matter‑of‑fact. In everyday speech, most people won’t feel a big difference here.

What case is долгим, and when do you use that case after был?