यह सेट मत हारिए।

A word-by-word breakdown is:

• यह = this
• सेट = set
• मत = don’t
• हारिए = lose / be defeated in a polite command form

So the whole sentence means Don’t lose this set.

In context, this is most natural in sports, such as tennis, badminton, or volleyball, where set is a normal term.

हारना is the dictionary form, meaning to lose or to be defeated.

In this sentence, the speaker is giving a command or instruction, so Hindi uses the imperative form instead of the dictionary form.

Here are some common imperative levels:

• हार — very blunt / not normally used by itself here
• हारो — informal
• हारिए — polite/respectful
• हारिएगा — even softer or more formal

So मत हारिए means please don’t lose or don’t lose in a respectful way.

मत is used to make a negative command in Hindi.

So:

• हारिए = lose / please lose
• मत हारिए = don’t lose

This is the normal way to say don’t do X in standard Hindi.

A very important point for learners:

• नहीं is usually used for statements: मैं नहीं हारता = I do not lose / I don’t lose
• मत is used for commands: मत हारिए = don’t lose

That is a very good question, because English lose has more than one meaning.

In Hindi, the choice depends on what kind of losing you mean:

• हारना = to lose in a contest, game, fight, election, match, set, etc.
• खोना = to lose in the sense of misplacing something or no longer having it

So in sports:

• यह सेट मत हारिए = Don’t lose this set

But if you were talking about losing your keys:

• चाबी मत खोइए = Don’t lose the key(s)

Because set here is a sports set, हारना is the correct verb.

Yes, सेट is very commonly used in Hindi as a borrowed word from English, especially in sports.

Hindi often keeps sports vocabulary from English, especially for terms like:

• सेट
• मैच
• गेम
• पॉइंट

So यह सेट मत हारिए sounds normal in a sports context.

A more idiomatic alternative in some situations could be:

• यह सेट मत गंवाइए।

Here गँवाना / गंवाना means something like to throw away, to let slip, or to lose carelessly, and it is also common in sports talk.

This is because यह is being used in its direct form.

In Hindi, demonstratives like यह and वह often change when followed by a postposition such as को, से, में, etc.

Compare:

• यह सेट = this set
• इस सेट को = this set
  • object marker को

So:

• यह सेट मत हारिए = correct
• इस सेट को मत हारिए = also possible, with को

The version without को is very natural. Hindi often leaves direct objects unmarked, especially when the meaning is already clear.

You do not need को here.

Both of these can be understood:

• यह सेट मत हारिए
• इस सेट को मत हारिए

The first one is simpler and very natural. The second one adds object marking and can feel a little more explicit.

In everyday Hindi, especially with inanimate nouns like सेट, leaving out को is completely normal.

Hindi word order is fairly flexible, but some orders sound more natural than others.

The most natural order here is:

• यह सेट मत हारिए।

You may also hear:

• सेट मत हारिए। = Don’t lose the set.
• यह मत हारिए। = Don’t lose this one.
  (only if the context already makes set obvious)

Putting मत directly before the verb is the most standard pattern:

• मत हारिए

So for learners, the safest pattern is:

[object] + मत + [verb]

हारिए is a polite imperative form. It can be used:

• for one person respectfully
• for more than one person
• in formal or polite speech

So this could be said to:

• a player you are addressing respectfully
• a group of players
• someone in a formal coaching or commentary-like tone

If you were speaking to a friend informally, you would more likely say:

• यह सेट मत हारो।

Here are some common versions:

• यह सेट मत हारो। — informal, to a friend or someone younger
• यह सेट मत हारिए। — polite/respectful
• यह सेट मत हारिएगा। — extra polite / softer / more formal

So the original sentence is in the middle: polite, but not extremely formal.

Yes, it is understandable and natural in a sports context.

That said, depending on tone and region, some speakers might also prefer:

• यह सेट मत गंवाइए।
• यह सेट मत हारो।
• इस सेट को मत गंवाइए।

The original sentence is perfectly fine, especially if someone is encouraging a player during a match.

The main thing is that हारना fits because this is about losing in competition, not misplacing an object.