A subordinating conjunction is a word that connects two thoughts by making one subordinate to the other.
To "subordinate" suggests making one statement less important than the other. Consider this example:
"Although some people tried to repair the tennis courts, they were unable to gain sufficient public backing."
The main idea, "they were unable to gain sufficient public backing," can stand alone because it is an independent clause (complete sentence); the subordinate idea, "Although some people tried to repair the tennis courts," cannot stand alone because it is a dependent clause (sentence fragment). Either clause may come first in the sentence.
A necessary transition is provided by a subordinating conjunction between any two ideas in the sentence. The time, place, or cause and effect relationship is indicated by this transition. Subordinating conjunction minimizes the importance of one clause. This helps the reader to understand which of the two ideas is more important. The main clause contains the more important idea, the less important idea belongs to the dependent clause that is introduced by subordinate conjunction.
Common Subordinating Conjunctions that are used are –
after, although, if, if only, though, till, as, in order that, unless, as if, now that, until, as long as, when, as soon as, once, rather than, whenever, where, since, as though, since, so that, because, whereas, than, wherever, before, even if, that, while, even though.
In general, subordinating conjunctions can be used in the following instances:
To show condition: we use subordinating conjunctions like “as if, though, even though, although, if, since, provided, less"
To show intent: we use subordinating conjunctions like “that, in order that, so that"
To show identification: we use subordinating conjunctions like “where, that, when, who, which"
To show time: we use subordinating conjunctions like “when, while, since, until, after, before"
To show cause: we use subordinating conjunctions like “because, since."
A subordinate clause is always preceded by a subordinating conjunction which means a subordinate clause is introduced by a subordinating conjuction.
However, a subordinate clause can sometimes come after and sometimes before a main clause.
Subordinate Clause(Dependent Clause) First:
Until you make up your mind, we won't be able to leave.
Although traffic was light every morning, the employee was unable to arrive at work on time.
Main Clause(Independent Clause) First:
The little girl overheard her parents arguing in the next room even though they were whispering.
Please retype this letter after you return from lunch.
Subordinating Conjunctions Versus Prepositions
A word such as "until", "before", "since", "till", or "after" can function as either a preposition or a subordinating conjunction, depending on its position in a sentence.
We can easily find out whether these words are acting as a subordinating conjunction or as a preposition.Recall that subordinating conjunctions, unlike prepositions, connect two complete ideas.
A subject and a verb follows a subordinate conjunction, forming a subordinate clause.
However preposition will have noun following the preposition.
Look at the following examples and you can clearly note the difference.
Since you are driving in that direction anyway, please drop this movie off at the video store.
Since this morning, I have had a headache.
After you finish reading that book, may I borrow it?
After lunch, I am going shopping for a new pair of shoes.
1) As she fell down on the road , the bus screeched to halt.
2) Someone keeps making loud noise whenever she falls asleep.
3) He searched in the shelf where she usually keeps her files.
4) Because she had severe headache, she left early from office.
5) Unless someone breaks the silence in the room, it would appear as if they are mourning.