Proper Use of The Semicolon

Pity the poor semicolon — so often misunderstood, so seldom asked to dance because he is seen as stiff, formal, and pretentious. But he’s such a practical, useful fellow whose talents should be appreciated that I would like to reintroduce him to you.

A semicolon has two primary functions, exemplified in two labels attached to it: It is said to be the equivalent of a weak period and a strong comma. Think of the two as distinct dance steps.

In its weak-period mode, the semicolon stands in for a period when an independent clause could appear as a separate sentence but is so closely related to the previous independent clause that the semicolon is inserted to signal that relationship: “An investigator files and locates court documents; librarians file claims for missing serials and locate requested information.”

As a stand-in for a strong comma, it separates items in a list when one or more items in that list are themselves lists: “The apple figures prominently in Christian and Islamic belief; Greek, Nordic, and Celtic legends; and folklore throughout the Western world.”

It serves that function, too, when one or more list items otherwise include a comma: “Astrology’s origins can also be traced to several other locations and cultures, including Egypt, which developed sophisticated timekeeping and calendar science; Greece, where Ptolemy authored influential astrological and astronomical texts; and Rome, where many of the most learned men — including two emperors — were astrologers who wrote laws and counseled citizens based on the stars.”

That said, though semicolons are underutilized in the first role, they are overused in the second — they’re underappreciated for their facility with one dance step and are too often called on to demonstrate the other dance step when the dance is not appropriate. Here are some solutions for balancing out the semicolon’s dance card:

1. “More than 900 million people still lacked access to clean drinking water in 2010; and 2.6 billion did not have adequate sanitation.”
An independent clause following a weak-period semicolon should not begin with a conjunction; they are redundant to each other. Often, the conjunction is preferable: “More than 900 million people still lacked access to clean drinking water in 2010, and 2.6 billion did not have adequate sanitation.” (This usage, common in the past, is frequently seen in classic literature, but it’s fallen out of favor.)

2. “Part of the company’s responsibility is to show others their responsibility; to help other water users see that small changes can save a lot of water.”
If a thought does not constitute an independent clause, use a comma (or, for greater emphasis, perhaps an em dash), not a weak-period semicolon: “Part of the company’s responsibility is to show others their responsibility, to help other water users see that small changes can save a lot of water.” (Again, easily found in older works, but no longer considered proper usage.)

3. “That is true, however, the increasing conflicts over water for energy involve the vast amounts power generation makes unavailable for people and aquatic ecosystems.”
Here is a weak-period construction complicated by the presence of the conjunctive adverb however, which requires a comma after it. The one before it should be a weak-period semicolon: “That is true; however, the increasing conflicts over water for energy involve the vast amounts power generation makes unavailable for people and aquatic ecosystems.”

4. “Residents had to slash their water use by a third, farmers by nearly half.”
Here’s a similar problem. The phrase “farmers by nearly half” is an incorrectly punctuated abridgement of the potential independent clause “farmers had to slash their water use by nearly half.” The elided repetition of the phrase “had to slash their water use” is signaled by a comma in its place, and the two independent clauses are stitched together by a weak-period semicolon: “Residents had to slash their water use by a third; farmers, by nearly half.”

5. “He also uses a Geiger counter, which measures radiation; motion detectors; barometric pressure monitors; and thermometers.”
This sentence is grammatically correct as is, but so many semicolons in a short sentence make it look cluttered. Reconstruct the sentence to eliminate the need for the strong-comma semicolons: “He also uses a Geiger counter, which measures radiation, plus motion detectors, barometric pressure monitors, and thermometers.”

6. “Our services can identify sites that infringe on brand name, content, or trademarks; misuse a brand name or image; or disparage a brand.”
Here’s another solution for the correct-but-excessive strong-comma semicolon — when only one item in a list is itself a list, if it’s logical to do so, move that item to the end of the sentence: “Our services can identify sites that disparage a brand, misuse a brand name or image, or infringe on brand name, content, or trademarks.”

7. “Follow-up studies are needed to improve our understanding of whether influences on decision making carry through to patterns of actual disclosure; whether involvement in counseling affects outcomes; and whether access to professional assistance at the time of planned disclosure is helpful.”
Semicolons are not required to separate items in a list just because one or more items is lengthy, especially in this sentence, in which the repetition of whether clearly signals the beginning of each list item. Replace the strong-comma semicolons with authentic commas: “Follow-up studies are needed to improve our understanding of whether influences on decision making carry through to patterns of actual disclosure, whether involvement in counseling affects outcomes, and whether access to professional assistance at the time of planned disclosure is helpful.”