Here's why:
* Clarity: Conjunctions act like signposts, indicating the relationship between the clauses. For example, "because," "while," and "although" tell us about the cause, contrast, or time relationship.
* Grammar: Some adverbial clauses require a conjunction to be grammatically correct. For instance, a clause starting with "since" or "although" needs to be connected to the main clause with a conjunction.
Examples:
* Without a conjunction: *I went to the store, I needed milk.* (This sentence is grammatically correct but could be clearer.)
* With a conjunction: *I went to the store because I needed milk.*
However, there are some situations where a conjunction is not necessary:
* Short, simple clauses: *The sun set, the sky turned orange.* (This is grammatically correct and clear without a conjunction.)
* Implied relationship: *He ran fast, winning the race.* (The relationship between the clauses is implied by the sentence structure.)
In general, using a conjunction to introduce an adverbial clause is a good practice. It helps to make your writing more concise, clear, and grammatically correct.