В нашем офисе работает уборщица, которая приходит рано утром.

In our office there is a cleaning lady who comes early in the morning.

Breakdown of В нашем офисе работает уборщица, которая приходит рано утром.

• в: in
• рано: early
• утро: the morning
• работать: to work

Questions & Answers about В нашем офисе работает уборщица, которая приходит рано утром.

Why does the sentence start with В нашем офисе instead of Уборщица, like in English?

Russian often puts the known background information first and the new or important information later.

• В нашем офисе работает уборщица focuses on the fact that in our office there is a cleaner (existential meaning: “In our office, there works a cleaner”).
• Уборщица работает в нашем офисе would focus more on the cleaner (e.g. “The cleaner works in our office (not somewhere else)”).

So starting with В нашем офисе sounds natural when you are introducing the existence of this cleaner in your office for the first time.

What case are нашем and офисе, and how do we know which endings to use?

Нашем and офисе are in the prepositional case (also called locative), used after в when it means “in/inside” a place.

• Nominative: наш офис – our office (dictionary form)
• Prepositional: в нашем офисе – in our office

Patterns:

• Masculine/neuter adjectives: наш → в нашем (ending -ем)
• Masculine nouns like офис: офис → в офисе (ending -е)

So: preposition в (meaning “in a place”) + question “где?” (where?) → use prepositional case: в нашем офисе.