A sentence is made of a subject and a predicate. Those terms aren’t on our parts of speech list, so let’s find out what they mean.

Subjects and Predicates

The subject is the thing or person that is doing the action in the sentence. Since nouns refer to things and people, the subject is a noun or pronoun, but it can also be modified by an article or adjective.

The predicate is everything else. The most important part of the predicate is the verb; you can’t have a sentence without a verb.

In the examples below, the subject is underlined, the verb is bolded, and the predicate is italicized.

Example: The dog runs.

Example: I am eating cake.

Example: The blue car drove down the dusty road.

As you can see, all you need for a sentence is a subject and a verb, but you can have a longer predicate as well.

Imperative sentences, which issue a command, are often just a verb, but they have an implied subject.

Example: Stop! = [You] stop!

Independent and Dependent Clauses

The example sentences that I’ve given so far are also independent clauses. An independent clause has a subject, a verb, and is a complete thought. In contrast, a dependent clause is not a complete thought, even though it also has a subject and a verb.

Independent Example: I studied grammar today

Dependent Example: While I studied grammar today

Independent Example: Writing is hard work

Dependent Example: Because writing is hard work

An independent clause can stand by itself and be a complete sentence, but a dependent clause needs to join with an independent clause to make a sentence.

When you join the two types of clauses together, follow these rules (the independent clause is blue and the dependent clause is red):

Dependent + Comma + Independent

Example: While it was raining, I baked cookies.

Example: Since you are funny, I want to be friends.

Independent + Dependent

Example: I’m busy studying because my exam is tomorrow.

Example: I felt sick after I ate all that chocolate.

Basically, if the dependent clause is first, you need a comma before the independent clause, but no comma is needed if the independent clause goes first. The exception is relative clauses, which are covered here.

Sentence Problems: Comma Splices and Fused Sentences

Now you know how to join a dependent clause to an independent clause, but what about joining two independent clauses together?

Some writers try to join independent clauses using the same techniques that we just learned, but they are wrong. Joining two independent clauses with a comma is called a comma splice.

Wrong: There are so many rules about sentences, I’m confused.

Another mistake is joining two independent clauses together with no punctuation. This is called a fused sentence.

Wrong: There are so many rules about sentences I’m confused.

Now, we need to find the solution to these problems. You have three options when joining independent clauses:

  1. Use a comma and a coordinating conjunction (those are the FANBOYS, remember)
  2. Use a semicolon
  3. Use a semicolon, a conjunctive adverb, and a comma

Right: There are so many rules about sentences, so I’m confused.

Right: There are so many rules about sentences; I’m confused.

Right: There are so many rules about sentences; therefore, I’m confused.

Sentence Problems: Fragments

Remember, a dependent clause needs an independent clause to be a complete sentence. If you have a dependent clause by itself, then it’s a sentence fragment.

Example: Although I love swimming.

Example: Because of the weather.

A sentence expresses a complete thought, but sentence fragments leave you wondering, “Although what? Because of what?”

Because online writing is informal and conversational, sometimes it’s okay to use sentence fragments, which are used in informal speech. Since they’re grammatically incorrect, sentence fragments stand out. If you choose to use a fragment, make sure that you have a good reason and aren’t just being lazy.

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