मेरा मन काम में नहीं है।

Because मन is a masculine singular noun in Hindi.

So the possessive adjective has to agree with मन:

• मेरा मन = my mind / my heart / my inclination
• not मेरी मन

A quick comparison:

• मेरा मन — correct
• मेरी किताब — correct, because किताब is feminine

So in this sentence, मेरा is matching मन, not काम.

Here, मन does not just mean mind in a strictly intellectual sense. It often means something like:

• mind
• heart
• mood
• inclination
• inner willingness / interest

So मेरा मन काम में नहीं है suggests:

• my mind is not in the work
• I’m not mentally engaged in the work
• I don’t feel like working
• I’m not in the mood for work

It is a very common Hindi word that often covers both emotional and mental state.

Because the grammatical subject here is मन, not मैं.

The sentence is structured around मेरा मन = my mind.

So Hindi is effectively saying:

• My mind is not in the work

Since मन is third-person singular, Hindi uses है, not हूँ.

Compare:

• मैं थका हूँ। = I am tired.
• मेरा मन थका है। = My mind/heart is tired.
• मेरा मन काम में नहीं है। = My mind is not in the work.

काम में literally means in work.

The postposition में often means in, inside, or within, but in many expressions it has a more idiomatic sense. Here, काम में होना suggests being mentally involved or engaged in the work.

So:

• काम में = in the work / engaged with the work
• मेरा मन काम में है = my mind is in the work
• मेरा मन काम में नहीं है = my mind is not in the work

This is similar to English expressions like:

• My heart isn’t in it
• My mind isn’t on the job
• I’m not into the work right now

In Hindi, नहीं usually comes before the verb or verb phrase it negates.

So:

• है = is
• नहीं है = is not

That is why the sentence is:

• मेरा मन काम में नहीं है

and not:

• मेरा मन काम में है नहीं in standard neutral Hindi

A few more examples:

• वह घर में नहीं है। = He/She is not at home.
• मुझे समझ नहीं है। = I don’t have understanding / I don’t understand that well.
• मेरा ध्यान नहीं है। = My attention is not there.

It can suggest either, depending on context, but usually it points more to lack of mental engagement or mood than a direct refusal.

Possible shades of meaning include:

• I’m not in the mood for work.
• I can’t focus on work.
• My heart isn’t in the work.
• I don’t feel like working.

If you want to say a clearer I do not want to work, Hindi would more directly use something like:

• मैं काम नहीं करना चाहता/चाहती। = I do not want to work.

So the original sentence is softer and more about state of mind.

Yes, it is understandable and natural, though many speakers might also say a slightly fuller expression such as:

• मेरा मन काम में नहीं लग रहा है।

That means something like:

• my mind is not settling into the work
• I am unable to get into the work
• I can’t concentrate on the work

The sentence you were given, मेरा मन काम में नहीं है, is shorter and still natural. It gives the idea that your mind or interest is simply not there.

The difference is mainly in nuance.

• मेरा मन काम में नहीं है
  = My mind is not in the work.
  This describes a general state.

• मेरा मन काम में नहीं लग रहा है
  = My mind is not getting engaged in the work / I’m unable to focus on the work.
  This sounds more dynamic and often more conversational.

The verb लगना in this kind of expression often suggests:

• getting attached
• becoming engaged
• settling into something

So मन लगना is a very common expression for to feel engaged / to take interest / to settle into something.

Yes, Hindi word order is somewhat flexible, especially for emphasis.

The neutral version is:

• मेरा मन काम में नहीं है।

You may also hear:

• काम में मेरा मन नहीं है।

This puts more emphasis on काम में — as for work, my mind is not in it.

Both are understandable. The first version is the most straightforward and neutral for learners.

Sometimes, but not always with exactly the same feeling.

• मन is very common for mood, inclination, interest, inner feeling, willingness
• दिल is more literally heart, and often sounds more emotional

In a sentence about work, मन is the more natural choice.

• मेरा मन काम में नहीं है = very natural
• मेरा दिल काम में नहीं है = understandable, but usually less idiomatic in this context

English often says My heart isn’t in my work, but Hindi usually prefers मन for this kind of idea.

No, this sentence stays the same:

• मेरा मन काम में नहीं है।

That is because मेरा agrees with मन, and मन is masculine singular no matter who is speaking.

So both a man and a woman can say:

• मेरा मन काम में नहीं है।

By contrast, in a sentence with a participle or adjective agreeing with the speaker, gender might change. For example:

• मैं थका हूँ। = male speaker
• मैं थकी हूँ। = female speaker

But in your sentence, nothing changes because the agreement is with मन.

You can use the same pattern with many other things.

Examples:

• मेरा मन पढ़ाई में नहीं है। = My mind is not in studying.
• मेरा मन बातों में नहीं है। = I’m not mentally present in the conversation.
• मेरा मन खेल में नहीं है। = I’m not into the game.
• मेरा मन कहीं और है। = My mind is somewhere else.

So this is a useful structure:

• मेरा मन + X में + नहीं है

meaning:

• my mind/interest is not in X

A word-by-word breakdown is:

• मेरा = my
• मन = mind / heart / inclination
• काम में = in work
• नहीं = not
• है = is

So very literally:

• My mind in work not is

Natural English:

• My mind is not in the work
• I’m not in the mood for work
• I can’t focus on work
• My heart isn’t in my work

The exact English wording depends on context, but the Hindi structure is very straightforward once you see that मन is the grammatical subject.