4 | Unusual Places Where You Need to Use a Comma

Best Practices

Many people know that you need to routinely use a comma in certain places including (1) before a conjunction (and, but, or, nor, for, yet, so) to separate two independent clauses in a sentence (“proteins were quantified by Western blots, and DNA was extracted for Sanger sequencing”), (2) after introductory phrases such as “however” and “lastly”, and (3) to set off phrases or clauses that are not essential to the meaning of a sentence, both at the beginning and end of the phrase. Moreover, many people have already formed an opinion about serial commas, also known as Oxford commas, which are the commas inserted before the last item in a list of three or more items. Some people use these in all lists, whereas others do not (our editing program recommends the consistent use of the serial comma). Always use a serial comma when necessary for clarity (there is ambiguity in this sentence, “The scientists she admires most include her postdoctoral mentors, Elizabeth Blackburn and Marian Koshland”; the serial comma makes clear the author is referring to more than two people, “The scientists she admires most include her postdoctoral mentors, Elizabeth Blackburn, and Marian Koshland”).

Here are a few unusual places where the appropriate insertion of a comma will show off your impeccable writing style:

1. After the year in a date with a month, day, and year. For example, “The National Cancer Act signed into law on December 31, 1971,^[1] provided the necessary framework for today’s cancer center program, data collection efforts through SEER (Surveillance, Epidemiology, and End Results Program), and the National Clinical Trials Network.” No commas are needed when only the month and year are given or when writing the date in the British English style or international date format (31 December 1971).
2. After a geographic location with a city and state. For example, “Buffalo, New York, won a Golden Snow Globe award for being the snowiest city in the United States with over 100,000 residents during the winter of 2018–2019.”^[2]
3. Before and after a degree. For example, “Gerty Theresa Cori, née Radnitz, MD, was the first woman to win the Nobel Prize in Physiology or Medicine^[3] for her research on carbohydrate metabolism, much of which was carried out at Roswell Park (then the State Institute for the Study of Malignant Diseases) during the 1920s.”
4. In between coordinating adjectives (thoughtful, intelligent students) but not non-coordinate adjectives (bright green dye). Coordinate adjectives can be identified by the fact that you can reverse their order or write “and” in between them without changing the meaning.
5. After and around interjections. For example, “Indeed, the results supported the hypothesis that the protein is a viable target for anticancer therapies.”

Above are common places where people often get tripped up in their academic writing. For a more comprehensive refresher on commas, visit Purdue OWL’s (Online Writing Lab) website on Extended Rules for Using Commas.^[4]