A compound conjunction is a phrase used to connect two words or phrases together within a sentence. Unlike many other types that consist of only a single word, these phrases include two or more words together that function within a sentence to link words or clauses to each other. For example, the phrase "as well as" is a compound conjunction that is often used in a sentence like, "Mike, as well as his sister Sarah, stayed home sick from school this morning." In this example, the phrase "as well as" is used to connect the idea of "Mike" to "his sister Sarah," which function together as the subject of the sentence.
The function of a compound conjunction is similar to other types of conjunctions, though a phrase is used rather than a single word. Simple conjunctions usually require only a single word, such as "and" or "because." These types of words function within a sentence by connecting other words and phrases together, sometimes indicating something about the relationship between those connected ideas. The word "because," for example, is a subordinating conjunction that connects a subordinate clause to a main clause within a sentence. Additionally, "because" indicates a cause and effect relationship.
A compound conjunction works in much the same way, though it does not necessarily have to connect two particular types of clauses or phrases. The phrase "as well as" is one of the most common compound conjunctions, which can often be used in much the same way as "and." In a sentence like "Cats, as well as dogs, often like to have room to run around," the phrase simply connects the words "cats" and "dogs." The word "and" could be used in the place of this compound conjunction, making the sentence "Cats and dogs often like to have room to run around."
"And yet," is also a compound conjunction, though it is not quite as commonly used in modern English. This phrase can be found in a sentence like "I just got home from the store, and yet I forgot to buy milk." In this usage, not only does it connect two clauses together, but it indicates something about the relationship between them. It is often used to illustrate something ironic or contradictory, such as someone forgetting to purchase something even though the person was just at the store. The phrase "as if" is also a compound conjunction, and is used to indicate that one phrase or clause is acting as an example or illustration of an idea.