Learn Farsi: این داروی تسکین‌دهنده هیچ گران نیست، اما خیلی مفید است. - This soothing medicine is not expensive at all, but it is very useful.

In this sentence, hich acts as an adverb modifying the adjective gerân (expensive). When paired with a negative verb like nist, it changes from meaning "no" to meaning "not at all." So hich gerân nist translates perfectly to "is not expensive at all."

Could I use aslan instead of hich to mean "not at all" in this sentence?

Yes! You could say aslan gerân nist. While aslan is the most common way to say "not at all" in everyday conversation, using hich adverbially like this is a great alternative that adds a slight emphasis and sounds a bit more elevated.

The word taskin-dahande translates to "soothing." How is this compound word built?

It is made of two parts: taskin (meaning relief or alleviation) and dahande (the present participle of dâdan, meaning giving). Literally, it means "relief-giving." You will see the -dahande suffix used frequently to turn verbs into active adjectives, like neshân-dahande (showing or indicating).

Why isn't there a Farsi word for "it" before kheyli mofid ast in the second half of the sentence?

Farsi often drops subject pronouns when the subject is already obvious from the context. Since the first clause establishes in dâru-ye taskin-dahande as the subject, adding (it) right after is unnecessary and would actually sound a bit clunky to a native speaker.