यह पुस्तकालय है।

• यह = this
• पुस्तकालय = library
• है = is

So the structure is literally this library is, which corresponds to This is a library or This is the library, depending on context.

Hindi usually places the verb at the end of the sentence. That is one of the most basic word-order patterns in Hindi.

So instead of English This is a library, Hindi says:

• यह = this
• पुस्तकालय = library
• है = is

That gives This library is in literal order, but the natural English translation is still This is a library.

Hindi does not normally use articles like English a, an, and the.

So यह पुस्तकालय है। can mean:

• This is a library
• This is the library

Which one is meant depends on the situation.

If you are used to English, this can feel strange at first, but it is completely normal in Hindi.

यह usually means this.

It is the near demonstrative, used for something close to the speaker. Its partner is वह, which means that for something farther away.

A useful contrast:

• यह पुस्तकालय है। = This is a library.
• वह पुस्तकालय है। = That is a library.

In real speech, you will also often hear ये instead of यह.

In careful grammar books, यह is often transliterated as yah.

But in everyday pronunciation, many speakers say something closer to yeh.

So for a learner:

• spelling: यह
• common pronunciation: roughly yeh

This is very normal. Hindi spelling and everyday pronunciation do not always match perfectly.

A simple pronunciation guide is:

pus-ta-kaa-lay

More carefully:

• पु = pu
• स्त = st
• का = kaa
• लय = often pronounced roughly lay

So the whole word sounds approximately like pustakaalay.

This is a somewhat formal, Sanskrit-based word. In everyday conversation, many speakers instead say लाइब्रेरी for library.

It is a correct and standard Hindi word, but it sounds a bit formal or bookish to many learners.

In everyday speech, people often say:

• लाइब्रेरी = library

So both of these are possible:

• यह पुस्तकालय है।
• यह लाइब्रेरी है।

The first sounds more formal or textbook-like. The second is very common in speech.

है is the present-tense form of to be used with a singular subject in simple statements like this.

Here the sentence is talking about one thing: this.

So:

• यह पुस्तकालय है। = This is a library.

You would use हैं with plural or respectful subjects, for example:

• ये पुस्तकालय हैं। = These are libraries.
• आप शिक्षक हैं। = You are a teacher. / You are teachers.

Not clearly.

In यह पुस्तकालय है।, nothing changes to show gender. The noun पुस्तकालय is generally treated as masculine, but this sentence alone does not make that obvious.

You can see the gender more clearly with an adjective:

• यह पुस्तकालय बड़ा है। = This library is big.
  Here बड़ा shows masculine agreement.

If it were a feminine noun, the adjective would usually change:

• यह _ बड़ी है।

That mark is called the danda. It is the traditional sentence-ending punctuation mark used in Devanagari writing.

So:

• । in Hindi/Devanagari works like
• . in English

In modern informal writing, especially online, you may also see a regular period, but । is the standard mark.

Yes.

Because Hindi does not have articles like a and the, the exact English translation depends on context.

So the same Hindi sentence could be understood as:

• This is a library
• This is the library

If the listener already knows which library is being talked about, the library may be the best translation.

Very simply:

• क्या यह पुस्तकालय है? = Is this a library?
• यह पुस्तकालय नहीं है। = This is not a library.

So you can build from the original sentence by:

• adding क्या at the beginning for a yes/no question
• adding नहीं before है for negation