Learn Hardcore Russian: У нас будет семейный праздник.

У меня есть машина. – I have a car. (literally: At me there is a car.)
У них будет встреча. – They will have a meeting. (literally: At them there will be a meeting.)

So «У нас будет семейный праздник» is the natural Russian way to say “We will have a family celebration.”

Why do we say «У нас будет семейный праздник» and not «Мы будем иметь семейный праздник»?

The verb иметь (“to have”) is not usually used in everyday Russian to talk about people possessing things or having events.

Мы будем иметь семейный праздник is grammatically possible, but it sounds unnatural and even slightly formal/odd in this context.

Instead, Russian uses «у + genitive»:

У нас будет семейный праздник. – We will have a family celebration.
У него будет день рождения. – He will have a birthday (celebration).

Use иметь mostly:

in formal/written language (e.g., иметь право – “to have a right”),
in set expressions (e.g., иметь значение – “to have significance”).

For everyday “have” / “will have” with people, prefer the «у + genitive» construction.

What grammatical case is «нас» in, and why is that case used here?

«Нас» is the genitive plural form of мы (“we”).

Personal pronoun мы (we) declines like this:

Nominative: мы – we
Genitive: нас – of us
Dative: нам – to us
Accusative: нас – us
Instrumental: нами – with/by us
Prepositional: о нас – about us

The preposition у (“at, by, with (in terms of possession)”) always requires the genitive:

у меня – at me / I have
у тебя – at you (singular)
у него / у неё – at him / at her
у нас – at us / we have
у вас – at you (plural/formal)
у них – at them

So «у нас» literally means “at us”, which in this construction expresses possession or something happening with us (“we have / we will have”).

Why is the verb «будет» in the singular, not plural? Shouldn’t it agree with «нас» (“us”)?

The verb «будет» agrees with the subject, which is «семейный праздник» (“a family celebration”), not with «нас».

У нас будет семейный праздник.
– The subject is праздник (celebration, singular masculine).
– So we use 3rd person singular: будет (“will be”).

Think of the structure as:

[At us] [will be] [a family celebration].

If the subject were plural, the verb would be plural:

У нас будут семейные праздники.
– We will have family celebrations (plural).
– Subject: праздники (plural) → verb: будут (3rd person plural).

What exactly is «будет» grammatically? How is it formed?

«Будет» is the 3rd person singular future tense of the verb быть (“to be”).

Forms of быть in the simple future:

я буду – I will be
ты будешь – you will be (singular, informal)
он / она / оно будет – he/she/it will be
мы будем – we will be
вы будете – you will be (plural or formal)
они будут – they will be

In «У нас будет семейный праздник», the subject is «праздник» (“celebration”), which is 3rd person singular, so we use он будет → будет.

Literally: “At us there will be a family celebration.”

What case is «семейный праздник» in, and how can I tell?

«Семейный праздник» is in the nominative singular.

Reasons:

It’s the subject of the verb будет (what will be? → семейный праздник).
The adjective семейный ends in -ый, which is the typical masculine nominative singular ending.
The noun праздник is a masculine noun ending in a consonant, nominative singular form.

So together:

семейный (masculine nominative singular adjective)
праздник (masculine nominative singular noun)

→ семейный праздник = “a family celebration” as the subject.

Why is it «семейный праздник» and not «семейная праздник» or «семейное праздник»?

The form of the adjective must agree with the gender, number, and case of the noun it modifies.

праздник is masculine, singular, nominative.
Therefore, the adjective must also be masculine singular nominative: семейный.

Adjective endings in nominative singular:

Masculine: -ый / -ий – семейный праздник
Feminine: -ая / -яя – семейная традиция (a family tradition)
Neuter: -ое / -ее – семейное торжество (a family celebration, neuter noun)

So:

семейный праздник – correct (masculine noun)
семейная праздник – wrong (feminine adj + masculine noun)
семейное праздник – wrong (neuter adj + masculine noun)

Can we change the word order, like «Семейный праздник будет у нас»? Does it change the meaning?

Yes, you can change the word order:

У нас будет семейный праздник.
Семейный праздник будет у нас.

Both can mean essentially “We will have a family celebration.”

Nuance:

У нас будет семейный праздник.
– Neutral focus; you’re simply saying that we will have it.
Семейный праздник будет у нас.
– Puts more emphasis on where/with whom the celebration will be – “The family celebration will be at our place / with us (not somewhere else).”

In spoken Russian, word order is flexible and mainly used for emphasis, not for basic grammatical roles (which are shown by cases).

Does «У нас» mean “at our house” or “in our family”? How should I understand it here?

«У нас» can mean both, depending on context:

At our place / in our home / with us (physically)
- Сегодня у нас будет вечеринка.
  – There will be a party at our place today.
In our family / in our group / in our organization
- У нас в семье строгие правила.
  – In our family we have strict rules.
- У нас на работе новый начальник.
  – We have a new boss at work.

In «У нас будет семейный праздник», it most naturally means:

either “At our place there will be a family celebration,”
or “We (our family) are going to have a family celebration.”

Usually both ideas are implied: your family is having it, likely at your place.

How would I say this in the present, like “We are having a family celebration (today)”?

In the present, Russian usually drops the verb быть (“to be”) in simple nominal sentences.

So instead of something with есть, you’d typically say:

Сегодня у нас семейный праздник.
– Today we are having a family celebration.
(literally: Today at us [is] a family celebration.)

You almost never need есть here; «У нас есть семейный праздник» sounds odd if you mean “we’re celebrating today.” It would sound more like “we possess such a thing as a family celebration,” which is not the intended meaning.

For talking about an ongoing event today, just say:

Сегодня у нас семейный праздник.

What is the difference between «праздник», «вечеринка», and «торжество»? Could I use any of them here?

They all relate to celebrations, but with different nuances:

праздник
- General word for a holiday, celebration, festive occasion.
- Can be official (New Year, Christmas) or personal (birthday).
- У нас будет семейный праздник. – We’ll have a family celebration/holiday.
вечеринка
- Means party, usually informal, often smaller, may or may not be family.
- У нас будет вечеринка. – We’ll have a party (at our place).
торжество
- More formal, ceremonial celebration: a formal event, ceremony, festivity.
- У нас будет семейное торжество. – We will have a family celebration (sounds a bit more solemn/formal than праздник).

In your sentence, «семейный праздник» is neutral and common.
You could say «семейное торжество» if you want it to sound more official/formal; «семейная вечеринка» would sound like a more casual family party.

How would the sentence change if there were several family celebrations, not just one?

You would make both the noun and the verb plural:

У нас будут семейные праздники.
– We will have family celebrations. / There will be family celebrations with us.

Changes:

Verb:
- singular: будет (he/she/it will be)
- plural: будут (they will be)
Noun:
- singular: праздник
- plural: праздники
Adjective:
- singular masculine: семейный
- plural: семейные (for all genders in nominative plural)

So:

У нас будет семейный праздник. – one celebration
У нас будут семейные праздники. – multiple celebrations