ओह, दवा घर में है।

Hindi uses postpositions, not prepositions.

• English: in the house
• Hindi: घर में — literally house in

So में means in / inside / at, and it comes after the noun it relates to.

Hindi usually puts the main verb, or the verb to be, near the end of the sentence. That is why है comes last.

So the structure is:

• दवा = the medicine
• घर में = in the house / at home
• है = is

This verb-final pattern is very common in Hindi.

Hindi does not normally use articles like English a, an, and the. Whether something is definite or indefinite is usually understood from context.

So दवा can mean:

• the medicine
• a medicine
• sometimes just medicine

The situation tells you which meaning is intended.

Yes, दवा is a feminine noun.

It does matter in Hindi, but in this particular sentence you do not see it clearly because है does not change for masculine vs. feminine singular.

You would notice the feminine gender more with adjectives or some verb forms, for example:

• अच्छी दवा = good medicine
• नई दवा = new medicine

So the gender is important, even if this sentence does not show much of it.

Both can be possible, but they are not exactly the same.

• घर में = in the house, inside the home
• घर पर = at home, at the house/home as a location

In this sentence, घर में sounds a little more like the medicine is physically inside the house.
If you said दवा घर पर है, it would often mean the medicine is at home, not here with us.

So the difference is small, but में is a bit more inside/in, while पर is a bit more at.

Yes. Hindi word order is flexible, although not completely free. You can change the order to shift the focus.

For example:

• दवा घर में है।
  This can emphasize the medicine.

• घर में दवा है।
  This sounds more like there is medicine in the house or focuses on the house as the location.

Both are grammatical, but they do not feel exactly the same in emphasis.

है is used with a singular subject here because दवा is singular.

If the subject were plural, you would usually use हैं instead.

For example:

• दवा घर में है। = singular
• दवाएँ घर में हैं। = plural

So है = is, and हैं = are in this kind of sentence.

Yes, they are very close in meaning. Both mean medicine.

• दवा is very common and standard
• दवाई is also very common, especially in everyday speech

A learner will hear both. In many situations, they can be used interchangeably.

For example:

• दवा घर में है।
• दवाई घर में है।

Both sound natural.

In standard Hindi, you should keep है in a sentence like this. It completes the statement.

• दवा घर में है। = complete, natural sentence
• दवा घर में। = incomplete in normal standard Hindi

In very casual speech, people sometimes shorten things, but for learning correct Hindi, it is best to include है.