The lyrics to a song that’s been popular since 1944 tell us to accentuate the positive, eliminate the negative, and not to “mess with Mr. In-Between.” Scientific writing, however, benefits greatly from appropriate use of the “Mr. In-Between” of punctuation, the semicolon.
Semicolons represent a useful compromise when the goal is to link closely related sentences. (The compromise is between a comma and a period.)
“Avoid long sentences,” is the advice the University of Connecticut Writing Center offers to students. “Try to avoid writing more than one thought per sentence. Don’t run on.”
Still, closely related sentences sometimes ought to be linked. Why? The University of Leicester in Great Britain offers two reasons:
- To emphasize their relationship
- To vary the pace of the writing
The University of Connecticut Writing Center itself goes on to say, “Writing generally puts together complex items and shows how they relate. A semicolon is an economical way to join two sentences, and therefore two ideas, to illustrate their relationship.”
Semicolons are used to separate independent clauses when a simple coordinating conjunction (e.g., and, or, but) is not used and when separate sentences would be too abrupt. For example:
- Three soil samples were collected per plot; the samples were then homogenized and divided into three subsamples.
- Five strains were visualized by staining; three strains did not stain.
- Many of the forests had been affected by fire; some tree species were not observed in any plots.
When main clauses are joined by a conjunctive adverb (e.g., furthermore, however, thus, therefore) or by a coordinating conjunction (e.g., and, but, or, so, yet) and one of the clauses has internal punctuation or is very long, a semicolon is used to join the clauses.
- For five days, birds were trapped in mist nets and tagged; nevertheless, very few species were recorded.
- Baines argues that there has been an increase in the occurrence of pneumonia in the university’s female student population; however, Health and Recreation Center intake statistics do not support this observation.
- Pigments are responsible for the spectacular red, yellow, orange, purple, and other colors of fall leaves; and temperate deciduous forests, found in both the Northern and Southern hemispheres, are an optimal place to see these displays.
The CSE Manual further explains that semicolons are used to separate structurally parallel clauses:
- In men, the main causative factor is obesity; in women, estrogen deficiency.
The semicolon helps writers avoid creating run-on sentences (e.g., the stream supported 18 fish species the water quality was good for fishing) or comma splices (e.g., the stream supported 18 fish species, the water quality was good for fishing):
- The stream supported 18 fish species; the water quality was good for fishing.
- The semicolon is often underused; its correct use can enhance the clarity of your writing.
Another use for the semicolon is to separate items in a list when one or more of those items contain a comma.
- The speakers were: Dr. Sally Meadows, Biology; Dr. Fred Eliot, Animal Welfare; Ms. Gerri Taylor, Sociology; and Prof. Li Zhou, Chemistry.
- The four venues will be: Middleton Hall, Manchester; Highton House, Liverpool; Marsden Hall, Leeds; and the Ashton Centre, Sheffield.
- There are basically two stages in the test for the presence of Escherichia coli: culturing water samples, using Petri plates containing a nutrient medium; extracting DNA, fingerprinting strains for source tracking.
Appropriate use of the semicolon can help create coherence and flow in scientific writing, so don’t be afraid of this Mr. “In-Between!”