Radije ostajem kod kuće.

Radije is an adverb meaning rather or preferably. In sentences like this, it often corresponds to English I’d rather... or I prefer to....

It expresses a preference between options, even if the other option is not stated.

Ostajem is a conjugated verb form, while ostati is the infinitive.

In Serbian, a full sentence normally needs a finite verb, so you say ostajem = I stay / I am staying.

Here, ostajem is:

• 1st person singular
• present tense
• from the imperfective verb ostajati

So the sentence is built like:

• radije = rather
• ostajem = I stay / I’m staying
• kod kuće = at home

Ostajem comes from ostajati, the imperfective partner of ostati.

This matters because Serbian often distinguishes between:

• imperfective: ongoing, repeated, general
• perfective: completed, single whole event

Using ostajem sounds natural for a general present preference or a current choice. It is not focused on the action being completed, but on the idea of staying.

The perfective partner is ostati, whose present form would be ostanem. That form is usually not used for a plain everyday present in the same way.

Because Serbian usually does not need subject pronouns when the verb ending already shows who the subject is.

Ostajem clearly means I stay, so ja is unnecessary.

You can add ja for emphasis or contrast:

• Ja radije ostajem kod kuće. = I prefer staying home.
• This might imply contrast with someone else.

Kod kuće is the normal Serbian expression for at home.

Literally:

• kod often means at, by, near, with
• kuće is the genitive form of kuća = house

So literally it is something like at the house/home, but you should learn kod kuće as a fixed expression meaning at home.

It is one of the most common ways to say that idea in Serbian.

Because the preposition kod requires the genitive case.

So:

• nominative: kuća
• genitive: kuće

That is why you get:

• kod kuće

This is a very common pattern in Serbian: the preposition determines the case of the noun that follows it.

This is a very useful distinction:

• kod kuće = at home
• u kući = in the house

Kod kuće is the normal idiomatic expression for being at home in general.

U kući is more physical and literal: it emphasizes being inside the house/building.

So in this sentence, kod kuće is the natural choice.

The given word order is very natural:

• Radije ostajem kod kuće.

Putting radije first sounds smooth and neutral because it sets up the speaker’s preference right away.

Other word orders are possible, but they may sound more marked or put emphasis in different places, for example:

• Ja radije ostajem kod kuće. — emphasis on I
• Ostajem radije kod kuće. — possible, but less natural in many contexts

So for a learner, the original order is a very good default.

Both can express preference, but they are used a little differently.

Radije:

• shorter
• often means rather
• often implies a comparison between options
• very natural in everyday speech

Više volim:

• literally I like more / I prefer
• often used with nouns or clauses
• can sound a bit more explicit

For example:

• Radije ostajem kod kuće.
• Više volim da ostanem kod kuće.

Both are possible, but radije is especially neat and natural for I’d rather stay at home.

Usually, Radije ostajem kod kuće is the safer and more natural form for a plain present preference.

Ostanem is the present form of the perfective verb ostati, and perfective present forms in Serbian do not usually work like a normal everyday present in the same way that imperfective forms do.

If you want to express a one-time future choice, Serbian more naturally uses something like:

• Radije ću ostati kod kuće. = I’d rather stay at home.
• Radije bih ostao/ostala kod kuće. = I would rather stay at home.

So:

• ostajem = good for a present/general preference
• ću ostati / bih ostao/ostala = often better for a specific decision

It is neutral and completely natural in everyday Serbian.

It is not especially formal, but it is not slang either. You could use it in normal conversation without any problem.

So it is a very useful sentence pattern to remember.