There are particular places where skilled English writers are still likely to wrongly add or drop a comma
THE DIFFICULTY OF COMMAS
Punctuation is rarely considered in writing courses for advanced learners of English. Yet many aspects of it seem to give uncertainty to even the most skilled academic and professional writers. They have already inspired a number of punctuation posts within this blog, in particular 17. Colons versus Semi-Colons, 30. When to Write a Full Stop and 58. Optional Apostrophe Endings.
Commas are no less of a problem, perhaps because they have so many different uses. The normal way to approach the problems of commas is by listing these uses. However, because the aim of this blog is always to offer something slightly different, I wish to focus more on when commas should not be used than when they should. To start, though, it is useful to be briefly reminded of the main uses. We cannot just say that commas show a “pause”, since many pauses in English are signalled by either a different kind of punctuation or no punctuation at all (see 91. Pronunciation in Reading Aloud).
THE MAIN COMMA USES
1. Separating listed items in a sentence
(a) Archaeological investigations involve detailed, painstaking study.
Other kinds of list, which usually need and or or before the last listed item, have no commas if they comprise only two items, and commas between their items if they are longer – though the last comma, before and/or, is optional, e.g.:
(b) The largest word classes are nouns, verbs, adjectives(,) AND adverbs.
2. Separating verbs joined by a conjunction
This happens particularly when the conjunction begins the sentence, before both of the linked verbs (see 25. Conjunction Positioning), e.g.:
(c) IF you work hard, you will succeed.
When a conjunction comes between the two verbs, a comma is less likely unless the conjunction is one of the “coordinating” kind (and, but, so, (n)or, for, yet).
3. Acting (along with a second comma or a full stop) like brackets
This use is associated with preposition phrases at the start of a sentence (see 85. Preposition Phrases and Corresponding Adverbs), connectors and other sentence adverbs (see 40. Conjunctions versus Connectors and 121. Sentence-Spanning Adverbs), some relative pronouns (see 34. Relative Pronouns and Commas), some participles (see 52. Participles Placed Just After their Noun and 75. How to Avoid “Dangling” Participles), some types of list (see 54. Sentence Lists 1: Incidental), and nouns explaining other nouns (see 77. Apposition), e.g.:
(d) Augustus Caesar, the first Roman Emperor, came to power by winning a war.
COMMON PROBLEMS WITH COMMAS
One of the best-known comma problems is distinguishing them from full stops. However, I do not wish to discuss this ‘comma splice’ error here, as I think it is more a misconception about full stop usage than comma usage, which can be read about in the post 30. When to Write a Full Stop. Nor am I here repeating the comma uses described in 1. Simple Example-Giving, 34. Relative Pronouns and Commas, and 77. Apposition. Four other frequent comma mistakes are the following.
1. Using a Comma after a Long Subject
Verb subjects (see 12. Singular and Plural Verb Choices) can be long or short, but only long ones are a problem. Consider this example (underlined):
(e) The very last task at the end of the day was to lock all of the doors.
The main word in this subject – the one “agreeing” with the verb was – is task; the other words make the meaning of task more exact. There is no reason to add a comma after day at the end of this long subject. This position is not one of the three main comma positions listed above. Perhaps the reason why writers often feel a need to add a comma after a long subject is that in speaking we would normally pause there. This discrepancy between speech and writing is a good illustration of why looking for sentence pauses is an unreliable way to decide where to use a comma.
2. Forgetting the Second of Two Bracket-Like Commas
Here are some more examples of commas used like brackets:
(f) Toyota, the largest car company in the world, is Japanese.
(g) The English, unlike the French, spread butter on their bread.
(h) There are a few grammar rules, however, that are easy to remember.
(i) Napoleon introduced many reforms, some of which endure today.
The first three examples here have two commas bracketing the underlined words, but in (i) a full stop replaces the second comma because the bracketed words are at the end of the sentence. It is in sentences needing two commas that the second comma is likely to be forgotten. I use the word “forgotten” because I believe that most people who leave out the second comma do actually know that two commas are needed. A similar error occurs with quotation marks and brackets, which also usually come in pairs.
3. Using a Comma between “that” and Reported Speech
The kind of sentence where some writers feel a need to add a comma after that is as follows:
(j) Jones (2013, p. 34) argues that English comma usage is problematic.
All of the words after that here are indirect speech (see 127. When to Use Indirect Speech). We should not usually place a comma after this kind of that because it is a conjunction, a kind of word that nearly always forbids a following comma (see 40. Conjunctions versus Connectors and 153. Conjunction Uses of “that”). In standard spoken English, there is not even a pause after that – any pause is likely to be before it rather than after. A possible reason for the feeling that a comma ought to be placed after that is the influence of direct speech, where the reported words are written inside quotation marks without that, and a comma goes before them.
4. Introducing a list with a comma
A comma can go only before lists that are not the central information in a sentence (see 54. Sentence Lists 1). If a list is central, there should be either a colon or no preceding punctuation at all, depending on the completeness of the introductory words (see 55. Sentence Lists 2). Here is an example where no punctuation is necessary:
(k) *The traditional branches of engineering are, mechanical electrical and civil.
The list here (underlined) comes directly after a verb, so that its removal would leave an incomplete sentence. This makes the comma unnecessary. You could make the first part into a possible complete sentence (Engineering has three traditional branches … ), and then a colon would be advisable.
CORRECT COMMA USES THAT SEEM INCORRECT
Sometimes a comma comes between a subject and a verb, or after that, and yet it is not wrong. It is useful to understand how this can happen.
1. Correct Comma Use between a Subject and a Verb
When a subject ends with bracketed information it needs a comma after it. Here is an example:
(l) The twins, Antonio and Maria, were rewarded.
The comma after Maria is possible because there is also a comma before Antonio, making Antonio and Maria bracketed. This means that they are the same as the twins, so only two people were rewarded (see 77. Apposition). You could also have no comma after Maria yet keep the one after twins. That would mean a list was being given, so that Antonio and Maria were not the same people as the twins, and four people altogether were rewarded.
Knowing about such possibilities can assist reading as well as writing. Consider this sentence from a newspaper:
(m) The improvement in UK business performance, increased government spending … .
It is easy to believe the underlined words are the subject of the verb increased (meaning that business improvement caused government spending to increase). However, this must be wrong because of the comma. The correct interpretation is that all of the words above are an unfinished list. The word increased must therefore be a participle, used like an adjective to describe spending, and not a verb (see 52. Participles Placed Just After their Noun).
2. Correct Comma Use after “that”
Once again the bracketing use of commas has an effect. Consider this (bracketed words underlined):
(n) Experts believe that, if regular exercise IS UNDERTAKEN, heart disease WILL BE less likely.
The underlined words, being bracketed, need commas before and after. Because they also come directly after that, the first comma must go there. Not all types of bracketing are possible after that. The type shown above involves a conjunction (if, as, when, after etc) written before both of the verbs it joins (shown in capitals)1. Another type of bracketing that is possible is with preposition phrases (which have no verb). You could thus exchange the underlined words in (n) for with regular exercise.
PRACTICE EXERCISE (COMMA USAGE)
Decide where commas are possible below. To help you, the comma types needed in each sentence, along with the order of their occurrence, are indicated by the letters A (= listing), B (= conjunction-associated) and C (= bracketing). Answers are given afterwards.
1. When thought is given to the different possible means of transport particularly motor vehicles in villages towns and cities it seems obvious that cycling is by far the most sensible. (C, A, B)
2. Engaging in conversation consulting a dictionary or at any rate a phrasebook and doing grammar exercises are all important strategies for learning a foreign language and will it may not be a surprise to learn also develop other intellectual abilities. (A, C, B, C)
3. There is no evidence as far as one can tell that genetic factors are the main reason why human beings of a particular colour stature or body shape outperform other human beings in particular areas of expertise since environmental factors like upbringing and training which are very difficult to separate out are an alternative very plausible explanation. (C, A, B, C, A)
1. When thought is given to the different possible means of transport, particularly motor vehicles, in villages, towns(,) and cities, it seems obvious that cycling is by far the most sensible.
2. Engaging in conversation, consulting a dictionary, or at any rate a phrasebook, and doing grammar exercises are all important strategies for learning a foreign language, and will, it may not be a surprise to learn, also develop other intellectual abilities.
3. There is no evidence, as far as one can tell, that genetic factors are the main reason why human beings of a particular colour, stature(,) or body shape outperform other human beings in particular areas of expertise, since environmental factors(,) like upbringing and training, which are very difficult to separate out, are an alternative, very plausible explanation.
1Note that the combination that, if is a rare example of two conjunctions written next to each other.