Questions & Answers about У нас сегодня большой праздник.
The most natural translations are:
- We have a big celebration today.
- It’s a big holiday for us today.
Literally, the sentence is closer to At our place / for us, today [there is] a big holiday, but in English we express this idea with we have or it’s … for us.
У нас literally means at us / with us / by us.
- у = at, by, near
- нас = us (genitive case of мы – we)
Russian often uses the construction у + [person in genitive] to express:
- possession: У меня есть книга – I have a book (literally: at me there is a book)
- something happening in someone’s sphere/space: У нас праздник – We have a celebration / There is a celebration at our place / for us
If you said Мы сегодня большой праздник, it would be ungrammatical, because мы (we) is nominative and does not work with у. You need нас after у.