A subordinating conjunction is a word that connects a main clause to a subordinate clause. A main clause is an independent clause that can stand alone by itself as a sentence. In other words, a main clause does not need any additional information to operate as a sentence. For example, the sentence "The student failed the test" is an example of a main clause.

A subordinate clause is a dependent clause that adds some extra information to the main clause. These phrases cannot stand by themselves, and their meaning is dependent upon that of the independent clause. They are not sentences! For example, "because she didn't study" is not a complete idea worthy of being defined as a sentence. However, combine the two clauses, and we have "The student failed the test because she didn't study." A complete idea has been expressed, and enough information has been presented in order to fully explain the thought.

In English, there are lots of subordinating conjunctions, but the most common ones, along with a few examples of how subordinating conjunctions are used, are as follows:

·         after – He went home after visiting his father in the hospital.

·         although – He did not revise his work although he had a test  the next day.

·         as – As I listened to the song, the memories came flooding back to me.

·         as long as -  Mother told me she would be happy with my results as long as I worked hard.

·         because – He missed the school bus because he woke up late.

·         before – She went for a jog before she had her breakfast.

·         even if - Even if you needed the money, you should not have stolen it.

·         if – I will be delighted if I manage to score full marks for the test.

·         once – Once she makes up her mind, she will not change her decision.

·         now that – Now that you are old enough, I will teach you how to cycle.

·         since – We have been friends since we were five years old.

·         though – He went to the park though it was raining.

·         unless – You should be in school unless you are sick.

·         until – I do not play computer games until I have finished my homework.

·         when – When he is in a good mood, he will tell jokes.

·         where – He likes to go to restaurants where he can eat sumptuous meals.

while – The loving father looks at his daughter while she sleeps