The Subordinate Clause

Recognize a subordinate clause when you find one.

A subordinate clause—also called a dependent clause—will begin with a subordinate conjunction or a relative pronoun. Like all clauses, it will have both a subject and a verb.

This combination of words will not form a complete sentence. It will instead make a reader want additional information to finish the thought.
Here is a list of subordinate conjunctions:

Subordinate Conjunctions
after although as as if as long as as soon as as though because before even if even though how if	in case in order that insofar as just as no matter how now that once provided that rather than since so that than	that though till unless until when whenever where whereas wherever whether while why

Here are the relative pronouns:

Relative Pronouns
that which whichever	who whoever whom	whose whosever whomever

Now read these examples:

After Amy sneezed all over the tuna salad
After = subordinate conjunction; Amy = subject; sneezed = verb.
Once Adam smashed the spider
Once = subordinate conjunction; Adam = subject; smashed = verb.
Until Mr. Sanchez has his first cup of coffee
Until = subordinate conjunction; Mr. Sanchez = subject; has = verb.
Who ate handfuls of bran flakes with his bare hands

Who = relative pronoun (functioning as the subject); ate = verb.

Remember this important point: A subordinate clause cannot stand alone as a sentence because the reader is left wondering, "So what happened?" When a word group begins with a capital letter and ends with a period, you must include at least one main clause to complete the thought. Otherwise, you have written a fragment, a major error.

After Amy sneezed all over the tuna salad.
So what happened? Did Amy throw the salad down the garbage disposal or serve it on toast to her friends? No complete thought = fragment.
Once Adam smashed the spider.
So what happened? Did Belinda cheer him for his bravery or lecture him on animal rights? No complete thought = fragment.
Until Mr. Sanchez has his first cup of coffee.
So what happens? Is he too sleepy to work, or does he have a grumpy disposition? No complete thought = fragment.
Who ate handfuls of bran flakes with his bare hands.

So what happened? Were the roommates shocked, or did they ask him to pass the cereal box so that they could do the same? No complete thought = fragment.

Punctuate a subordinate clause correctly.

When you attach a subordinate clause in front of a main clause, use a comma:

Subordinate Clause + , + Main Clause.

Even though the broccoli was covered in cheddar cheese, Emily refused to eat it.
Unless Christine finishes her calculus homework, she will have to suffer Professor Nguyen's wrath in class tomorrow.

While Bailey slept on the sofa in front of the television, Samson, the family dog, gnawed on the leg of the coffee table.

When you attach a subordinate clause at the end of a main clause, you will generally use no punctuation:

Main Clause + Ø + Subordinate Clause.

Tanya did poorly on her history exam because her best friend Giselle insisted on gossiping during their study session the night before.
Jonathon spent his class time reading comic books since his average was a 45 one week before final exams.

Diane decided to plant tomatoes in the back yard where the sun blazed the longest during the day.

Punctuation gets tricky with adjective clauses.

An adjective clause is a subordinate clause that begins with a relative pronoun such as who, which, or that.
This type of clause requires no punctuation when it is essential and comma(s) when it is nonessential. How do you make that determination?
When the information in the clause clarifies a general noun, the clause is essential and will follow the same pattern that you saw above:

Main Clause + Ø + Essential Adjective Clause.

Nick gave a handful of potato chips to the dog that was sniffing around the picnic table.

Dog is a general noun. Which one are we talking about? The adjective clause that was sniffing around the picnic table clarifies which animal we mean. The clause is thus essential and requires no punctuation.
When the adjective clause follows a specific noun, the punctuation changes. The information in the clause does not have the same importance, so the clause becomes nonessential, requiring a comma to connect it.

Main Clause + , + Nonessential Adjective Clause.

Nick gave a handful of potato chips to Button, who was sniffing around the picnic table.

Button, the name of a unique dog, lets us know which animal we mean. The information in the adjective clause has diminished impact, which you indicate with the comma.
Adjective clauses can also interrupt a main clause. When this happens, use no punctuation for an essential clause. But if the clause is nonessential, separate it with a comma in front and a comma behind.
Read these examples:

After dripping mustard all over his chest, the man who was wearing a red shirt wished that he had instead chosen ketchup for his hotdog.

After dripping mustard all over his chest, Charles, who was wearing a red shirt, wished that he had instead chosen ketchup for his hotdog.

Use subordination to combine ideas effectively.

Writers use subordination to combine two ideas into a single sentence.
Read these two simple sentences:

Rhonda gasped. A six-foot snake slithered across the sidewalk.

Since the two simple sentences are related, you can combine them to express the action more effectively:

Rhonda gasped when a six-foot snake slithered across the sidewalk.

If the two ideas have unequal importance, save the most important one for the end of the sentence so that your readers remember it best.
If we rewrite the example above so that the two ideas are flipped, the wrong point gets emphasized:

When a six-foot snake slithered across the side walk, Rhonda gasped.