Academic writing tips: How to use Commas and Semicolons
Complex ideas are usually best communicated using simple and concise phrasing. However, in academic writing, sentences can easily become long and difficult to read. This article offers an explanation for how commas and semicolons can be used to break up and clarify your writing.
Commas are extremely versatile, and it would be quite possible to write thousands of words about them. However, their three main uses in academic writing can be summarised as:
- Clarifying meaning by separating or joining words and clauses,
- Separating items in a list, and
- Introducing quotations.
Separating and joining words/clauses
Two related sentences can be joined using a comma and a conjunction (such as ‘and’ or ‘but’). For example:
The reactants were mostly consumed, but the catalyst could be recovered from the resulting solution.
Without the comma and conjunction, these clauses could instead be written as two complete sentences. However, joining them together using ‘, but’ emphasises that they are contrasting and related.
Also note that the last sentence you have just read in the paragraph above (‘However, joining them together…’) was introduced with ‘However’. Commas are also commonly used in this way to separate an introductory word or phrase from the rest of a sentence. The first sentence in the paragraph above (‘Without the comma and…’) gives another example of this with a longer introductory clause.
Commas can also be used to ‘parenthetically’ separate non-essential parts of a sentence. For example:
The participants, who were selected at random, were each given a paper-based questionnaire.
In this sentence, the phrase enclosed by commas gives additional information; it could be removed, and the sentence would still make sense. Note that the commas are very important here: without them, the sentence would imply that only the randomly selected participants were given a questionnaire.
Separating items in lists
Commas are used to separate items in a list:
The elements examined were magnesium, calcium, and strontium.
Note: Style guides tend to disagree about whether there should be a comma before the final ‘and’ in a list; this is known as a ‘serial’ or ‘Oxford’ comma. An important thing to note here is that most international scientific contexts tend to favour the use of this comma. This is because it can often remove ambiguity but almost never causes it.
A comma can be used to introduce a direct quote from another author:
According to Baxter et al. (1996), ‘This method can also be applied to high-voltage systems.’
Note, however, that a comma is not needed if a short quotation fits into the grammatical structure of a sentence:
Baxter et al. (1996) suggest that such an approach ‘is entirely justified’.
Semicolons can be used to:
- Link closely related sentences, and
- Separate items in a list.
Linking closely related sentences
If two sentences are closely related, then they can be joined with a semicolon (;). This can help to highlight their connection:
The samples were washed with distilled water; this removed any remaining traces of salt.
Note that the parts of the sentence on either side of a semicolon should themselves be complete sentences; if you remove the semicolon and replace it with a full stop, both parts should make sense on their own.
In addition to the sentence you’ve just read, note that there are two more examples of this sentence construction using semicolons in the section about commas. These are presented here again for ease of reference and for reiteration through examples, with the semicolon bolded.
In this sentence, the phrase enclosed by commas gives additional information; it could be removed, and the sentence would still make sense.
Style guides tend to disagree about whether there should be a comma before the final ‘and’ in a list; this is known as a ‘serial’ or ‘Oxford’ comma.
Separating items in lists with commas
Semicolons can also be used to separate items in a list when one or more of them contains commas:
…where: B represents the magnetic field; E is the electric field; and a, b, and c are constants.
Note that here, the list is introduced with a colon (:) for clarity.
There are very specific rules associated with commas and semicolons; if used appropriately, they can eliminate ambiguity and help to make your writing easier to read.
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