خوب

In a sentence

• هوا امروز خیلی خوب است.

  The weather is very good today.

  Here, 'خوب' functions as an adjective describing the noun 'weather,' indicating its favorable condition.

• او همیشه خوب رفتار می‌کند.

  She always behaves well.

  In this sentence, 'خوب' is used as an adverb to describe the manner of behavior, meaning 'well.'

• شنیده‌ام که او در کار خودش خیلی خوب است.

  I have heard that he is very good at his job.

  Here, 'خوب' is an adjective complement used to assess someone's skill positively.