Commas separate parts of a sentence so the meaning is clear. Sentence structure determines their correct use. Show
A comma separates introductory words, phrases and clauses from the main clause of the sentence. Many introductory phrases can be moved to the end of sentences without changing the meaning. In these cases, you don’t need a comma before the phrase. This simpler structure can be easier to read.
Place a comma after adverbs and other introductory wordsUse a comma after introductory words, such as greetings and adverbs, or when addressing someone. Using an introductory word gives it emphasis.
You don’t need a comma after an introductory word if the sentence is very short. This minimises punctuation in very short sentences. Use a comma after phrases and clauses that change the whole sentenceUse commas after adverbial phrases and adverbial clauses. Adverbs – such as ‘first’ and ‘during’ – modify verbs, adjectives and other adverbs.
Conditional clauses are adverbial clauses (for example, beginning with ‘if’, ‘unless’ or ‘until’). They should also have a comma after them if they start the sentence.
Unless the consultation starts early, it will not finish on time. [A conditional adverbial clause] Avoid beginning a sentence with a string of numbers and datesUse a comma after an introductory phrase that ends with a numeral and is immediately followed by another numeral. It doesn’t matter how short the sentence is. Avoid this type of sentence structure because the string of numbers can be confusing.
There were 16.5 million people enrolled to vote in Australian elections on 18 April 2019. [This structure avoids stringing a number together with a date.]
On 18 April 2019, 16.5 million people were enrolled to vote in Australian elections. [This is grammatically correct but less readable.] Mark out non‐essential information within a sentenceCommas isolate information in a sentence when it isn’t essential to:
Within a sentence, use a pair of commas to separate non-essential or supplementary information. Always check for the second comma where there should be a pair. Generally, if you can take out part of the sentence and it is still grammatically correct, it should be between a pair of commas. Check carefully. Using comma pairs can completely change the meaning of a sentence.
The committee, said the secretary, was incompetent. [The committee was incompetent.] The committee said the secretary was incompetent. [The secretary was incompetent.] Elements that function as supplementary information include:
Set off non-essential clausesUse commas around clauses that add information but aren’t essential to the meaning of the sentence. Don’t use commas if the clause is essential for meaning. If you can remove the clause and your sentence means the same thing, it’s non-essential and should go between commas. Non-essential clauses are also called ‘non-restrictive’ or ‘non-defining’ clauses.
The business report, which the manager had edited, explained the agency’s strategy. [The main message is ‘The business report explained the agency’s strategy’. The clause ‘which the manager had edited’ gives more information, adding to the meaning. It doesn’t change the meaning.] Introduced pests, such as varroa mite, threaten Australian honey production. [All introduced pests threaten honey production. The varroa mite is just an example.] EssentialThe report that the manager had edited explained the agency’s strategy. [The clause ‘that the manager had edited’ is essential to the meaning because there is no other information in the sentence to identify what report is being referred to.] Introduced pests from South Asia threaten Australian honey production. [Only pests from South Asia threaten honey production. Other introduced pests don’t affect honey production.] Each of these examples separates a grammatical subject from its verb. This is a problem when the subject is overburdened with non-essential information. Check if you can rephrase the information to make it easier to follow. It is easier for people to read shorter sentences.
The report was tabled last week. It is about demographic changes in rural areas in Western Australia.
The report, detailing demographic changes in rural areas in Western Australia, was tabled last week. Place commas around nouns that define the same thing they followUse a pair of commas when you have 2 noun phrases next to each other that define the same thing.
The strike took place in Whyalla, South Australia, in June 2014. [The noun phrase ‘South Australia’ is between two commas because it is non-essential information. ‘South Australia’ adds to the meaning but doesn’t change the meaning.]
The strike took place in Whyalla, South Australia in June 2014. You should be able to take out the noun phrase between the comma pair and still have a grammatically correct sentence.
The sentence loses detail without the second noun phrase (Mx Lesley May), but it is still a full sentence. Separate questions tagged onto a sentenceQuestions can be tagged onto the end of sentences. Use a comma before a question that is part of the sentence.
Use commas with the phrase ‘for example’Generally, use a comma before and after the phrase ‘for example’ in a sentence.
Some colours, for example, are difficult for people with colour blindness to distinguish. If ‘for example’ begins a sentence, it is an introductory phrase. Follow it with a comma.
For example, some colours are difficult for people with colour blindness to distinguish. If you’re introducing a bullet list after ‘for example’, use a colon.
Some colours are difficult for people with colour blindness to distinguish, for example:
Don’t use commas with Latin shortened formsIf you use Latin shortened forms, such as ‘e.g.’ and ‘i.e.’, don’t follow them with a comma.
Exports of rare earths (e.g. lithium, europium) have soared.
Exports of rare earths (e.g., lithium and europium) have soared. Place commas between principal clauses joined together with a conjunctionUse commas to connect 2 or more principal clauses joined by a coordinating conjunction (‘and’, ‘or’, ‘but’, ‘so’). If they have different subjects, use a comma before the coordinating conjunction. Do not use this rule to create a sentence of more than 25 words. Shorter sentences are easier to read.
The Senate debated the Bill at length, but the party whips eventually called for a vote. [‘But’ is the coordinating conjunction. ‘The Senate’ and ‘the party whips’ are each the subjects of a principal clause.] If 2 clauses share the same subject, you don’t need to repeat the subject or insert a comma before the conjunction.
The company closed its Perth office and sacked the chief financial officer. [‘The company’ closed an office and sacked an executive officer. ‘The company’ is the subject of both clauses, joined using ‘and’.] The exception to this rule is when you have joined more than 2 principal clauses with the same subject.
The company closed its Perth office, sacked the chief financial officer, and opened a branch in Singapore. [The verbs ‘closed’, ‘sacked’ and ‘opened’ each complement the same subject: ‘the company’. Each complement completes a principal clause.] Don’t use commas to ‘splice’ sentencesDon’t use a comma to link 2 stand-alone sentences unless you use a coordinating conjunction. This kind of error is called a ‘comma splice’.
The report was finished last week, but the minister has not approved its release.
The report was finished last week, the minister has not approved its release. Punctuate sentence lists and strings of adjectivesSeparate items in lists of nouns or adjectives with commasUse commas between items in a sentence list. Avoid using a comma before the last item in the list. This rule applies to sentence lists and sentence fragments in bullet lists. Do not punctuate the end of a list item with a comma if it is in a bullet list.
Restrict the use of the Oxford commaIf the last item combines two words or phrases with the word ‘and’, use a comma before that final item. This use of the comma is known as the ‘Oxford comma’ or ‘serial comma’.
The industries most affected are retail trade, wholesale trade, and accommodation and food services. [‘Accommodation and food services’ is listed as a single industry category. It is set off in the list with an Oxford comma.] The Oxford comma can prevent ambiguity in complex sentence lists. For example, use the Oxford comma before the last item if you’re using a defining phrase applicable only to that final item. A defining phrase is essential to the meaning of the sentence. The following examples show how the Oxford comma can affect meaning, using the defining phrase ‘for stockfeed’.
The analysis outlined demand for barley, wheat and hay for stockfeed. [All crops are for stockfeed.] The analysis outlined demand for barley, wheat, and hay for stockfeed. [Only the hay is for stockfeed.] Separate adjectives of the same typeWhen writing strings of adjectives, use a set order – evaluative, descriptive, then definitive. Use commas in strings of adjectives of the same type (for example, a string of descriptive adjectives).
Don’t use commas in strings of adjectives of different types.
Use commas in numbers with 4 or more digitsNumbers with 4 or more digits (starting from 1,000) need a comma. Use commas for numerals in text and in tables. You need to use a combination of words and numerals for large rounded numbers over a million. Large rounded numbers are punctuated with a decimal point.
Don’t use a space between the digits, because screen readers can read them as separate numbers.
The agency handles around 6,500 complaints each year.
The agency handles around 6 500 complaints each year. [This can be read as the number 6 followed by the number 500.] When you are using numbers of 1,000 or more, use commas to separate the numerals into groups of 3 (working right to left). Commas are not used to the right of a decimal point. Don’t use commas in postcodes or dates.
Show direct speech or quoted material using commasIntroduce directly quoted speech with a comma. Use the comma in combination with quotation marks.
If an attribution comes after a quotation, use a comma at the end of the quotation and before the quotation mark.
If the quotation is broken into 2 parts, the second part should follow a full stop rather than a comma.
If the quotation ends the sentence, end it with the original punctuation of the quotation.
The digital edition consolidates information from the sixth edition. It departs from advice in the sixth edition about the position of commas and quotation marks in sentences interrupted by expressions like ‘she said’. The sixth edition recommended the comma be outside the quotation mark. The digital edition recommends the comma be inside the quotation mark. The Content Guide had brief information about using a comma in sentences and with numbers. It had basic information on using quotation marks. It advised against using Oxford commas.
Oxford University Press (2016) ‘9.2 Layout of quoted text’, New Oxford style manual, Oxford University Press, Oxford. University of Chicago (2017) ‘6.40 Commas with quotations’, Chicago manual of style, 17th edn, University of Chicago Press, Chicago. ReferencesDixon JC and Bolitho B (2005–2019) Course notes and exercises: editing and proofreading for the workplace, Centre for Continuing Education, Australian National University, Canberra. Murphy EM with Cadman H (2014) Effective writing: plain English at work, 2nd edn, Lacuna, Westgate. Seely J (2001) Oxford everyday grammar, Oxford University Press, Oxford. Stilman S (2004) Grammatically correct, Writer’s Digest Books, Ohio. Truss L (2003) Eats, shoots and leaves: the zero tolerance approach to punctuation, Profile Books, London, 2003. |