AEM Academy

Complex Sentence Essentials and Subordinate Clauses

The basic unit of meaning is a clause. A clause consists of a subject and predicate, and a sentence is composed of one or more clauses.

  • A simple sentence has one independent clause, which just means a clause that makes sense by itself.
  • A compound sentence has two or more independent clauses joined together by coordinating conjunctions.
  • A complex sentence is composed of independent and dependent clauses.

1. Simple sentence

The technical term for a simple sentence is an independent clause. “Independent” just means that it can stand by itself as a sentence – it makes sense on its own.

  • A clause is a subject and predicate combo.
  • A subject is a noun – it’s what the sentence is about.
  • The predicate is the verb and the stuff after the verb – it’s what happens to the subject.


These are the three most common independent clause, or simple sentence, structures:

a) A very simple sentence can have a subject + verb:

  • She runs.

b) A common sentence structures is a subject + verb + object (an object, like a subject, is a noun):

  • Karl loves donuts.

c) Another one is a subject + verb + preposition phrase:

  • Ji Su commutes by subway.

2. Compound sentence

When we join two or more independent clauses together with a coordinating conjunction, we call it a compound sentence. There are six coordinating conjunctions that we use today, all of them two and three letter words. Conjunctions are joining words. These are the most basic and common ones: so, or, yet, but, and, nor (SOY BAN).

Compound sentence = Ind. clause + Coordinating conjunction + Ind. clause

  • Coordinating conjunction: so, or, yet, but, and, nor (SOYBAN)


Let’s turn our simple sentences into compound sentences:

  • She runs and she swims.
  • Karl loves donuts but he eats too many.
  • Ji Su commutes by subway so she doesn’t need a car.

3. Complex sentence

In both simple sentences and compound sentences, we’ve been dealing with one or more independent clauses. A simple sentence is a single independent clause. A compound sentence is two or more independent clauses joined together using a coordinating conjunction (SOYBAN: so, or, yet, but, and, nor).

Now let’s get to dependent clauses.

Just like an independent clause, a dependent clause also has a subject and a predicate, but it doesn’t make sense on its own. That’s why it’s called a dependent clause. The most common type of dependent clause is a subordinate clause. A subordinate clause looks like an independent clause, but it begins with a subordinating conjunction:

Independent clause: She runs every day.                

  • This makes sense on its own.

Dependent clause: because she runs every day

  • This doesn’t make sense on its own.

A dependent clause needs an independent clause to make sense:

  • She feels good because she runs every day.                

Subordinate Clauses

Subordinate clauses are the easiest way to improve your writing. They allow you to add details to almost any part of the sentence. Subordinate clauses begin with subordinating conjunctions. These are a few common constructions:

  • Because it's raining, I brought an umbrella.
  • Although it's raining, I still want to go out.
  • I don't answer the phone while I'm eating dinner.
  • Whenever it rains, I like to get a hot chocolate.

Note that the subordinate clause can go before or after the independent clause.

We can turn any of our independent clauses into a subordinate clause by adding a subordinating conjunction at the beginning of the independent clause. However, we can’t leave this by itself - if you leave this by itself, you’ve got a sentence fragment. We have to add an independent clause, and then we’ve got a complex sentence. As a reminder, a complex sentence consists of an independent clause and a dependent clause, and in this case, our dependent clause is a subordinate clause.

  • Independent clause: They ate dinner.
  • Subordinating conjunction: While
  • Subordinate clause: While they ate dinner
  • Independent clause: They watched a movie.
  • Complex sentence: While they ate dinner, they watched a movie. OR They watched a movie while they ate dinner.*

*Note that the subordinate clause can come before or after the independent clause. If the subordinate clause comes first, put a comma after it. If the subordinate clause comes after the independent clause, you usually don’t need a comma.

Can you start a sentence with “because?”

Yes. You can put a subordinate clause before or after an independent clause. It’s up to you which comes first, so yes, you can start a sentence with “because”.

Because she runs every day, she feels good.

She feels good because she runs every day.

Subordinating conjunctions

Subordinate clauses begin with subordinating conjunctions:

  • after, before
  • although, even though, though
  • as, as if, as soon as, as though
  • at the same time as
  • because
  • before
  • even as, even if
  • if
  • in case
  • no matter what
  • once
  • rather than
  • regardless of what
  • since
  • so that
  • unless 
  • until
  • whatever
  • whatsoever
  • when, whenever
  • where, whereas, wherever
  • whether
  • while

Subordinate clause placement & punctuation

Subordinate clauses are generally added to the beginning or end of a sentence, but you can also add them in the middle of a sentence. Because it’s less common, using them in the middle of a sentence is considered higher level writing than just placing them at the beginning or end of a sentence.

If the subordinate clause starts the sentence, put a comma after it. If the subordinate clause is after a short independent clause, you don’t need a comma. With a longer independent clause followed by a subordinate clause, it’s up to you whether to use a comma after the independent clause. You have to trust your ears: will a comma help the reader understand what’s going on?

This is a consistent grammar rule. If you place any modifier before the independent clause, use a comma after it (like in this sentence). You don’t need a comma if you put a modifier after the independent clause (like in this sentence). You can HEAR the punctuation. You pause at the comma when reading aloud. Use your ears:

Adverb

  • Yesterday, I went to bed at 11 PM.
  • I went to bed at 11 PM yesterday.

Preposition phrase  

  • In the final step, you should write a conclusion.   
  • You should write a conclusion in the final step.    

Subordinate clause  

  • Because it’s cold, we’re staying in.
  • We’re staying in because it’s cold.


Check out this complex sentence with one independent clause and two subordinate clauses. Note how many ways it can be arranged:

  • Because this medicine has toxic side effects, we don’t recommend it unless the situation is dire.
  • Unless the situation is dire, we don’t recommend this medicine because it has toxic side effects.
  • Because this medicine has toxic side effects, we don’t recommend it unless the situation is dire.
  • Because this medicine has toxic side effects, unless the situation is dire, we don’t recommend it.
  • Unless the situation is dire, because this medicine has toxic side effects, we don’t recommend it.
  • We don’t recommend this medicine because it has toxic side effects, unless the situation is dire.
  • We don’t recommend this medicine unless the situation is dire because it has toxic side effects.

Biggest sentence structure problems: sentence fragments (SF) and run-on sentences (ROS)

Sentence fragment (SF)

A sentence fragment is part of a sentence – it’s not a complete sentence.  These are fragments:

  • Dependent clauses: Because it was cold.
  • Preposition phrases: In the morning.

Neither of these makes sense on its own. They need an independent clause to make sense:

  • Because it was cold, I wore a sweater.
  • In the morning, I drink coffee.

Run-on sentence (ROS)

A run-on sentence (ROS) breaks the rules of how we can put sentences together: You can’t join two independent clauses together using a comma. Use a coordinating conjunction between them.

ROS: I love pizza, I shouldn’t eat too much.

Fix #1 = compound sentence: I love pizza but I shouldn’t eat too much.

Fix #2 = complex sentence: Although I love pizza, I shouldn’t eat too much.

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