Writing and Style Basics
3 | Break up Looooong Sentences
Key Point
Best Practices
Long sentences can be difficult to read, especially when the content is technical or complex. The readability of your manuscript or grant proposal will be enhanced immensely if lengthy blocks of text are broken up into smaller fragments that are easier for readers to digest. Several grammatical tools are available for breaking up the sentence structure, including periods, semicolons, and em dashes.
The simplest approach is to use a period to separate independent clauses when the sentence becomes long and unwieldy. While there is no straightforward rule to how long a sentence should be—variation in sentence length can actually make writing more interesting—sentences that are longer than 20–25 words can pose challenges to reader comprehension. Hence, scrutinize sentences that are longer than two or three lines to determine if these can be made shorter.
Use a semicolon to break up a rambling sentence when it makes sense to retain some sort of connection between the independent clauses. In the example below, Charles Darwin used a semicolon in the last sentence of On the Origin of Species,[1] which was written in 1859:
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
Finally, use an em dash to interject ideas and information that deserve more emphasis than a parenthetical phrase or fragment set off by commas—this type of dash is especially helpful when the interjected material contains commas. Em dashes are longer than hyphens and en dashes, and these symbols can be inserted by using the Insert > Symbol function in Microsoft Word. As shown below, Douglas Hanahan and Robert Weinberg artfully used em dashes in their seminal paper titled “Hallmarks of Cancer: The Next Generation” in Cell:[2]
The six hallmarks of cancer—distinctive and complementary capabilities that enable tumor growth and metastatic dissemination—continue to provide a solid foundation for understanding the biology of cancer.
Readers will benefit from your efforts to simplify the text by breaking up long, unwieldy sentences.[3]
- Darwin, C. & Kebler, L. (1859). On the origin of species by means of natural selection, or, The preservation of favoured races in the struggle for life. London: J. Murray. [Pdf] Retrieved from the Library of Congress. https://www.loc.gov/item/06017473/ ↵
- Hanahan, D. & Weinberg, R.A. (2011). Hallmarks of Cancer: The Next Generation. Cell, 144, 646–647. https://doi.org/10.1016/j.cell.2011.02.013 ↵
- This content would be useful for a training exercise in which participants are asked for their ideas on how to apply the above three tools to break up a long, rambling sentence that might appear in a scientific paper or grant proposal. ↵
