Many people consider semicolons to be the most confusing of the punctuation marks. These people generally fall into two camps: those who liberally pepper their page with semicolons, and those who never use them for fear of using them incorrectly. However, as with the other marks of punctuation, using semicolons is not difficult if you keep some basic rules in mind.
Rule 1: Use a semicolon between independent clauses that are closely related in theme.
Independent clause: a word group that contains at least one subject, at least one verb, and expresses a complete thought. An independent clause is also called a sentence.
The key words in this rule are closely related in theme. You should not place semicolons indiscriminately between independent clauses, as in the following example:
Example 1: Jane drove to Phoenix to visit her parents; her parents' dog had to go to the vet.
Clearly, these sentences have nothing to do with each other. The fact that Jane visited her parents in Phoenix is one thing, and the fact that her parents' dog had an appointment with the vet is quite another. A period should be used between unrelated sentences such as these. Semicolons should be placed only between sentences that are closely related in theme, as in the following example:
Example 2: Tom earned his bachelor's degree last summer; his sister earned hers in the fall.
These sentences are related thematically; both discuss academic degrees and when they were earned, so the semicolon is appropriate. Of course, a period would also be appropriate.
Rule 2: Use a semicolon before conjunctive adverbs and transitional phrases that join independent clauses.
Conjunctive adverb: adverb that acts as a transition between independent clauses by showing comparison, contrast, cause-effect, sequence, or other relationships.
Common conjunctive adverbs: also, consequently, conversely, finally, furthermore, hence, however, meanwhile, moreover, nevertheless, nonetheless, otherwise, similarly, subsequently, therefore, thus
Transitional phrase: a phrase that acts as a transition between independent clauses by showing comparison, contrast, cause-effect, sequence, or other relationships.
Common transitional phrases: after all, as a matter of fact, as a result, for example, in addition, in conclusion, in other words, on the contrary, on the other hand
Example 3: Philip is studying engineering; however, he is also interested in pursuing a degree in music education.
Example 4: Cindy has published several novels; in addition, she has published a volume of poetry.
In each of the previous two examples, you should note two things. First, the sentences joined by the semicolons are closely related in theme, which is the fundamental rule of semicolon placement. Second, note that the semicolon is placed before the conjunctive adverb or transitional phrase. This is because the adverb or phrase begins an independent clause. Compare the following examples:
Example 5: Angela fell and injured her leg last month; nevertheless, she was able to compete in the race today.
Example 6: Jim has always been an exceptionally hard worker; his coworkers, moreover, have nominated him for employee of the month seven times.
In Example 5, the semicolon is placed before the conjunctive adverb nevertheless since the adverb begins an independent clause. In Example 6, the semicolon is placed before his since his signals the beginning of the independent clause. The conjunctive adverb in this sentence (moreover) is simply serving as an interrupter.
Rule 3: To ensure clarity, use a semicolon between items that contain internal punctuation.
Compare the following examples:
Example 7: For her young son's birthday, Jenny purchased a chocolate cake with chocolate frosting, sprinkles, and candy topping, a pair of shoes with white stripes, laces, and light-up heels, and a new racetrack complete with cars, people figurines, and miniature buildings.
Example 8: For her young son's birthday, Jenny purchased a chocolate cake with chocolate frosting, sprinkles, and candy topping; a pair of shoes with white stripes, laces, and light-up heels; and a new racetrack complete with cars, people figurines, and miniature buildings.
Example 7 is difficult to read due to its excessive use of commas; because of the internal punctuation within each item in the list, the commas between those items serve only to muddle the writing and confuse the reader.
Example 8, which places semicolons between each item, is much clearer.
Semicolons are like spices; they shouldn't be overused. As spices complement the main ingredients in a dish, semicolons should complement your writing—not overpower it. When used correctly, semicolons can add variety and increased readability to your writing.