When you want to use commas and semicolons in sentences and when you are concerned about whether a sentence is or is not a fragment, a good way to start is to be able to recognize dependent and independent clauses. The definitions offered here will help you with this.

Independent Clause

An independent clause is a group of words that contains a subject and verb and expresses a complete thought. An independent clause is a sentence.

Dependent Clause

A dependent clause is a group of words that contains a subject and verb but does not express a complete thought. A dependent clause cannot be a sentence. Often a dependent clause is marked by a dependent marker word.

Dependent Marker Word

A dependent marker word is a word added to the beginning of an independent clause that makes it into a dependent clause.

Some common dependent markers: after, although, as, as if, because, before, even if, even though, if, in order to, since, though, unless, until, whatever, when, whenever, whether, and while.

Connecting independent clauses

There are two types of words that can be used as connectors at the beginning of an independent clause: coordinating conjunctions and independent marker words.

1. Coordinating Conjunction

The seven coordinating conjunctions used as connecting words at the beginning of an independent clause are and, but, for, or, nor, so, and yet. When the second independent clause in a sentence begins with a coordinating conjunction, a comma is needed before the coordinating conjunction:

2. Independent Marker Word

An independent marker word is a connecting word used at the beginning of an independent clause. These words can always begin a sentence that can stand alone. When the second independent clause in a sentence has an independent marker word, a semicolon is needed before the independent marker word.

Some common independent markers: also, consequently, furthermore, however, moreover, nevertheless, and therefore.

Connecting dependent and independent clauses

Subordinating conjunctions allow writers to construct complex sentences, which have an independent clause and a subordinate (or dependent) clause. Either clause can come first.

Note that the clauses are separated with a comma when the dependent clause comes first.

Some common subordinating conjunctions: after, as, before, once, since, until, and while.

Some Common Errors to Avoid

Comma Splices

A comma splice is the use of a comma between two independent clauses. You can usually fix the error by changing the comma to a period and therefore making the two clauses into two separate sentences, by changing the comma to a semicolon, or by making one clause dependent by inserting a dependent marker word in front of it.

Fused Sentences

Fused sentences happen when there are two independent clauses not separated by any form of punctuation. This error is also known as a run-on sentence. The error can sometimes be corrected by adding a period, semicolon, or colon to separate the two sentences.

Sentence Fragments

Sentence fragments happen by treating a dependent clause or other incomplete thought as a complete sentence. You can usually fix this error by combining it with another sentence to make a complete thought or by removing the dependent marker.