बारी आने पर सर्विस कीजिए।

Literally, it means something like on the turn coming or upon the turn arriving.

More naturally in English, it means:

• when your turn comes
• when it is your turn
• when your turn arrives

Breakdown:

• बारी = turn
• आने = coming / to come
• पर = on / upon / when

So बारी आने पर is a very common Hindi way to say when the turn comes.

Because पर is attached to the oblique infinitive form of the verb, not the basic dictionary form.

With आना (to come):

• dictionary form: आना
• oblique infinitive: आने

So:

• आने पर = on coming / when it comes

This pattern is common in Hindi:

• करने पर = on doing / when done
• जाने पर = on going / when one goes
• मिलने पर = on meeting / when one meets

So बारी आने पर is grammatically the normal form.

Here पर means something like on, upon, or more naturally when.

In this structure, verb + ने/ने-like oblique infinitive + पर often gives the meaning:

• when X happens
• upon X happening

So:

• बारी आने पर = when the turn comes
• घर पहुँचने पर = when you reach home
• समय मिलने पर = when time is available / when you have time

This is a compact, natural Hindi structure. English often uses when, but Hindi often uses ...ने/आने/करने पर.

Because सर्विस is an English loanword, and in Hindi many borrowed nouns combine with करना (to do) to form a verb-like expression.

So:

• सर्विस करना = to do service / to serve

In this sentence, the imperative polite form of करना is used:

• कीजिए = please do

So:

• सर्विस कीजिए = please serve / please do the service

This pattern is very common in modern Hindi, especially with English-derived words:

• फोन कीजिए = please call
• स्टार्ट कीजिए = please start
• चेक कीजिए = please check

कीजिए is a polite or respectful imperative.

It is commonly used when speaking:

• respectfully
• formally
• to customers, strangers, elders, or politely in public settings

Compare:

• करो = do (informal)
• कीजिए = please do (polite)
• करिए = also polite, very close in meaning to कीजिए

So सर्विस कीजिए sounds like a polite instruction: Please serve.

Yes, usually that is understood from context.

बारी by itself means turn, and Hindi often leaves out words like your if they are obvious.

So बारी आने पर can naturally be understood as:

• when your turn comes
• when the turn comes

If the speaker wants to make it explicit, they could say:

• अपनी बारी आने पर सर्विस कीजिए।

That more clearly means:

• When your turn comes, please serve.

So the original sentence is normal and natural, especially if the context already makes it clear whose turn is meant.

Yes. Hindi word order is flexible, though some orders sound more natural than others.

The original:

• बारी आने पर सर्विस कीजिए।

is very natural because the time/condition comes first, then the instruction.

You could also say:

• सर्विस बारी आने पर कीजिए।

This is still understandable, but it feels a bit more marked or less straightforward.

A very natural alternative is:

• अपनी बारी आने पर सर्विस कीजिए।

So yes, the word order can shift, but the original order is smooth and idiomatic.

Yes. A sentence with जब is also possible.

For example:

• जब बारी आए, तब सर्विस कीजिए।
• जब आपकी बारी आए, सर्विस कीजिए।

These mean roughly the same thing: when your turn comes, please serve.

The difference is mostly stylistic:

• बारी आने पर is more compact
• जब ... feels a little more explicit, like a full when clause

Both are correct, but ...आने पर is a very common concise structure.

In modern spoken Hindi, yes, English loanwords are extremely common, and सर्विस can be used naturally depending on the context.

However, the exact naturalness depends on what kind of service/serve is meant. In some situations, speakers may prefer another word or phrase.

But grammatically, सर्विस कीजिए is perfectly normal Hindi structure:

• English-origin noun + करना

So even if the vocabulary is borrowed, the grammar is very Hindi.

The sentence has two parts:

1. बारी आने पर = a time/condition phrase

   • when the turn comes

2. सर्विस कीजिए = the main polite command

   • please serve

So the full pattern is:

• [When X happens] + [polite command]

This is a very useful Hindi structure:

• मौका मिलने पर बताइए। = Tell me when you get a chance.
• समय आने पर देखिए। = Look at it when the time comes.
• ज़रूरत पड़ने पर फोन कीजिए। = Call if needed / when needed.

So this sentence is a good example of a common Hindi way to give instructions tied to a condition or time.