डाक टिकट लिफ़ाफ़े पर है।

A word-by-word breakdown is:

• डाक = mail, post
• टिकट = ticket, stamp
• डाक टिकट = postage stamp
• लिफ़ाफ़े = envelope (in its oblique form)
• पर = on
• है = is

So the sentence structure is basically:

डाक टिकट + लिफ़ाफ़े पर + है
= The postage stamp + on the envelope + is

This is a very common question, and it is an important grammar point.

The basic dictionary form is लिफ़ाफ़ा = envelope.
But when a masculine singular noun ending in -ा is followed by a postposition like पर (on), it usually changes into the oblique form.

So:

• लिफ़ाफ़ा = envelope (direct form)
• लिफ़ाफ़े = envelope (oblique form)

Because the sentence says on the envelope, Hindi uses:

• लिफ़ाफ़े पर

This is similar to what happens with many masculine nouns:

• कमरा → कमरे में = in the room
• लड़का → लड़के के साथ = with the boy
• लिफ़ाफ़ा → लिफ़ाफ़े पर = on the envelope

पर means on.

In English, words like on, in, under, with usually come before the noun, so they are called prepositions:

• on the envelope

In Hindi, these words come after the noun, so they are often called postpositions:

• लिफ़ाफ़े पर
• literally: envelope on

This is why the noun often changes into the oblique form before a postposition.

Hindi normally prefers Subject–Object/Complement–Verb order, so the verb often comes last.

In English:

• The stamp is on the envelope.

In Hindi:

• डाक टिकट लिफ़ाफ़े पर है।
• literally: The stamp on the envelope is.

This verb-final pattern is very normal in Hindi. As a learner, it helps to expect the main verb near the end of the sentence.

है is the singular present form of to be here, meaning is.

Since डाक टिकट is singular, Hindi uses है:

• डाक टिकट लिफ़ाफ़े पर है। = The stamp is on the envelope.

If the subject were plural, you would usually use हैं:

• डाक टिकटें लिफ़ाफ़े पर हैं। = The stamps are on the envelope.

So है matches a singular subject.

It is written as two words, but together they function as one expression:

• डाक = post/mail
• टिकट = ticket/stamp
• डाक टिकट = postage stamp

Hindi often combines nouns this way, where the first noun describes the second. English does this too:

• post office
• coffee cup
• school bus

So डाक टिकट is a natural compound meaning postage stamp.

Hindi usually does not use articles the way English does.

English requires:

• a stamp
• the stamp

Hindi often just says:

• टिकट
• डाक टिकट

The exact meaning—a stamp, the stamp, or sometimes just stamp—is understood from context.

So डाक टिकट लिफ़ाफ़े पर है। can mean:

• The postage stamp is on the envelope and, depending on context,
• A postage stamp is on the envelope

In many beginner translations, English uses the because it sounds most natural.

This order is the most neutral and standard:

• डाक टिकट लिफ़ाफ़े पर है।

Hindi word order is somewhat flexible, especially in speech, because postpositions and context make the roles fairly clear. For emphasis, a speaker might rearrange things, but the standard learner-friendly order is best.

For example, लिफ़ाफ़े पर डाक टिकट है may also be understood, with a slightly different emphasis, like There is a stamp on the envelope.

So yes, word order can vary somewhat, but the given sentence is the safest basic pattern to learn.

लिफ़ाफ़े is pronounced roughly like li-faa-fe.

A useful breakdown:

• लि = li
• फ़ा = faa
• फ़े = fe

The letter फ़ is a borrowed sound used for f. In very careful pronunciation, it is different from फ, which traditionally is more like an aspirated p sound. In modern speech, many speakers pronounce फ and फ़ similarly, especially in casual conversation.

So for a learner, pronouncing लिफ़ाफ़े with a clear f sound is a good goal.

Yes, nouns in Hindi have grammatical gender, but in this sentence it does not cause many visible changes.

• लिफ़ाफ़ा is masculine
• टिकट is generally treated as masculine in common usage
• डाक by itself is feminine, but in the compound डाक टिकट, the full expression behaves as a noun phrase meaning postage stamp

In this sentence, the main visible grammar point is not gender but:

1. the oblique form लिफ़ाफ़े
2. the singular verb है

Gender becomes more noticeable in other contexts, especially with adjectives and past-tense verbs.

You would replace पर (on) with में (in):

• डाक टिकट लिफ़ाफ़े में है।

Notice that लिफ़ाफ़ा still becomes लिफ़ाफ़े, because में is also a postposition, so the noun still has to be in the oblique form:

• लिफ़ाफ़ा → लिफ़ाफ़े में

So:

• लिफ़ाफ़े पर = on the envelope
• लिफ़ाफ़े में = in the envelope

Sometimes yes, but it depends on context.

टिकट by itself can mean many kinds of ticket:

• train ticket
• movie ticket
• entry ticket
• stamp, in some contexts

If you want to be completely clear that you mean a postage stamp, डाक टिकट is better.

So:

• टिकट = ticket/stamp, depending on context
• डाक टिकट = specifically postage stamp

In a sentence about letters and envelopes, टिकट might still be understood, but डाक टिकट is more precise.