Parentheses are most often used to identify material that acts as an aside (such as this brief comment) or to add incidental information.
Other punctuation marks used alongside parentheses need to take into account their context. If the parentheses enclose a full sentence beginning with a capital letter, then the end punctuation for the sentence falls inside the parentheses. For example:
Typically, suppliers specify air to cloth ratios of 6:1 or higher. (However, ratios of 4:1 should be used for applications involving silica or feldspathic minerals.)
If the parentheses indicate a citation at the end of a sentence, then the sentence’s end punctuation comes after the parentheses are closed:
In a study comparing three different building types, respirable dust concentrations were significantly lower in the open-structure building (Hugh et al., 2005).
Finally, if the parentheses appear in the midst of a sentence (as in this example), then any necessary punctuation (such as the comma that appeared just a few words ago) is delayed until the parentheses are closed.
You can also use parentheses to provide acronyms (or full names for acronyms). For example, “We use the MLA (Modern Language Association) style guide here” or “The Modern Language Association (MLA) style guide is my favorite to use.”
Remember, parentheses always appear in pairs. If you open a parenthesis, you need another to close it!
In technical writing, there are additional rules for using parentheses, which can be more nuanced. While we won’t discuss those rules here, it’s important to bear their existence in mind, especially if you’re considering going into a more technical field.
Have the parentheses been used correctly in the following sentences? Correct any errors you find.
- (Escobar et al., 2014) wrote about this phenomenon in their most recent paper.
- NASA (National Aeronautics and Space Administration) just announced three new initiatives.
- Michael lost the wrestling competition. (He also lost his temper).
- Helena took the chocolate bars (her favorites) and gave Davi the sour candies.
- No. Even parentheses are only used to cite information at the end of a sentence. A corrected version of the sentence would look something like these:
- Escobar et al. wrote about this phenomenon in their most recent paper (2014).
- A recent paper discussed this phenomenon (Escobar et al., 2014).
- Yes. Parentheses can be used to enclose the full name of an acronym.
- No. The second sentence is entirely in parentheses, so the period should be inside as well.
- Michael lost the wrestling competition. (He also lost his temper.)
- Yes. The phrase her favorites is a brief aside that can be enclosed by parentheses.
Brackets are a fairly uncommon punctuation mark. Their main use is in quotations: they can be used to clarify quotes. For example, say you want to quote the following passage:
“I finally got to meet Trent today. I had a really great time with him. He was a lot taller than expected, though.”
However, you only want to relay the fact that Trent was taller than the speaker expected him to be. In order to do this, you would write the following: “[Trent] was a lot taller than expected.”
The brackets let the reader know that while the word Trent wasn’t in the original quote, his name was implied there. When using brackets, you need to be careful not to change the original meaning of the quote.
Another use of brackets is when there is a spelling or informational error in the original quote. For example, “Gabriel sat down on the river bank to fed [sic] the ducks.” (The term sic means that the typo was in the original source of this quote.)
Read the following passages. Imagine you want to quote the numbered sentences. Each sentence would appear separately. Use brackets to indicate the best way to do so.
(1) Mont Vesuvius is a stratovolcano in the Gulf of Naples, Italy, about 5.6 mi east of Naples and a short distance from the shore. It is one of several volcanoes which form the Campanian volcanic arc. (2) It consists of a large cone partially encircled by the steep rim of a summit caldera caused by the collapse of an earlier and originally much higher structure.
(3) Mount Vesuvius is best known for its eruption in CE 79 that led to the burying and destruction of the Roman cities of Pompeii, Herculaneum, and several other settlements.
- Mont Vesuvius [sic] is a stratovolcano in the Gulf of Naples, Italy, about 5.6 mi east of Naples and a short distance from the shore.
- [Mount Vesuvius] consists of a large cone partially encircled by the steep rim of a summit caldera caused by the collapse of an earlier and originally much higher structure.
- This quote would not need any brackets.