यह एलर्जी की दवा का बिल है।

Both की and का are forms of the Hindi genitive marker, which is often like of or sometimes for in English.

In this sentence:

• एलर्जी की दवा = medicine for allergy
• दवा का बिल = bill for the medicine

So the full structure is:

• [एलर्जी की दवा] = allergy medicine
• [एलर्जी की दवा का बिल] = bill for allergy medicine

Hindi often connects nouns this way instead of using a separate word like for.

Because दवा is a feminine noun, and the genitive marker agrees with the noun that follows it.

So:

• का is used with masculine singular nouns
• की is used with feminine nouns
• के is used with masculine plural nouns and in some other situations

Since दवा is feminine, you say एलर्जी की दवा.

Because बिल is treated as a masculine noun in Hindi. The genitive marker agrees with बिल, not with दवा.

So:

• दवा का बिल = the bill of/for the medicine

Even though दवा is feminine, that does not matter here. What matters is the gender of the noun after का/की/के, which is बिल.

Good question. Hindi often uses का/की/के in noun chains where English might use for.

So English says:

• bill for allergy medicine

Hindi says more literally:

• allergy's medicine's bill

That sounds strange in English, but it is natural in Hindi.

So का/की/के can sometimes feel like of, and sometimes like for, depending on the phrase.

Hindi usually builds noun phrases from left to right toward the main noun, and the main identifying word often comes later.

Here the order is:

• यह = this
• एलर्जी की दवा का बिल = allergy medicine bill
• है = is

So literally it is something like:

• This allergy-medicine bill is

Natural English reverses that as:

• This is the bill for allergy medicine

Hindi is often more head-final than English, meaning the important noun or verb tends to come later.

है means is.

It is the present-tense form of to be used with a singular subject here.

So:

• यह ... है = This is ...

Without है, the sentence would sound incomplete in standard Hindi.

It is a borrowed word, ultimately from English allergy, but it is very common in modern Hindi. Hindi uses many borrowed words, especially for modern life, medicine, technology, and administration.

So learners should not be surprised to see words like:

• एलर्जी
• बिल
• डॉक्टर
• फोन

These are normal in everyday Hindi.

Yes. दवा and दवाई both mean medicine. In many contexts they are interchangeable.

So you may also hear:

• यह एलर्जी की दवाई का बिल है।

That would sound natural too.

No, Hindi does not have articles in the same way English does.

So बिल can mean:

• a bill
• the bill

The exact meaning depends on context.

In this sentence, English naturally uses the bill or sometimes simply the bill for the allergy medicine, but Hindi does not need a separate word for that.

Literally, the structure looks like that, but the actual meaning is simply the bill for the allergy medicine.

Hindi often uses possession-like structures for relationships that English expresses in different ways. So you should not translate too mechanically.

A more word-for-word gloss might look like:

• यह = this
• एलर्जी की दवा = allergy medicine
• का बिल = bill of/for
• है = is

Natural meaning: This is the bill for the allergy medicine.

A simple pronunciation guide is:

yah allergy kee dawaa kaa bill hai

More carefully:

• यह = yah or yeh
• एलर्जी = allergy
• की = kee
• दवा = davaa
• का = kaa
• बिल = bill
• है = hai

A natural full reading is:

Yeh allergy ki dawa ka bill hai.

Yes, but it would be a bit more explicit and usually less compact.

For example:

• यह एलर्जी की दवा के लिए बिल है
  or
• यह एलर्जी की दवा का बिल है

The second version is more natural for a simple label or identification: This is the bill for the allergy medicine.

Hindi often prefers the shorter noun-chain structure unless there is a reason to be extra clear.