An adverb is a word that modifies a verb, adjective, or another adverb. They typically end in -ly, but using too many of them can make your writing sound choppy. What makes an adverb relative is that it is completely dependent on the phrases that come before it.
Relative clauses are usually less formal. They include where, when, why, whatever, and wherever. These replace the formal structures of relative clauses, which begin with a preposition and which. For example, see the following:
- I know the park where he likes to go when the weather is good.
- The day after tomorrow when I finally get to move into my new apartment is going to be great!
- Sarah knows the reason why I feel so tired every week.
For the first sentence, where replaces the more formal to which. It could be changed to “I know the park to which he likes to go when the weather is good.” For the second sentence, when replaces the more formal on which. That sentence would be “The day after tomorrow on which I finally get to move into my new apartment is going to be great”. The third sentence shows why replacing for which. In a more formal setting, the sentence would read: “Sarah knows the reason for which I feel so tired every week”.