Lists that are the main point of a sentence usually follow either a colon or a verb with no punctuation
THE PROBLEM OF LIST-GIVING
Lists are common in academic and professional writing, where there is a regular need to give such listable information as aims, reasons, results, similarities, differences, examples, subclasses, problems, solutions, conclusions and recommendations. Unfortunately, grammar errors are also common in list-giving by writers whose mother tongue is not English. Many of these comprise a chapter in my book Grammar Practice for Professional Writing.
Part of the challenge in list-giving is writing the words around it, and part is putting the list itself into the right grammatical form. The surrounding words vary according to whether the list is given in a single sentence or as bullet points or in multiple sentences, and in single-sentence listing according to whether or not the list is the main information being given. This post is about the words around a list when it is the main information of a single sentence.
The wording around single-sentence lists that are not the main information being given is the topic of the Guinlist post 54. Sentence Lists 1: Incidental, while words accompanying bullet-point lists are in 74. Sentence Lists 3: Bullet Points. The problems of composing lists themselves, whether in sentences or as bullet-points, are the topic of the post 93. Good and Bad Lists. Advice on introducing and composing multi-sentence lists is offered in 122. Signpost Words in Multi-Sentence Lists. One other relevant post is 17. Colons versus Semi-Colons.
WAYS OF INTRODUCING A MAIN-MESSAGE SENTENCE LIST
There are essentially two different ways to introduce a list that is the main information of a single sentence. Compare the following (the lists are underlined):
(a) The (two) main languages of South America are Spanish and Portuguese.
(b) There are three basic branches of Biology: Botany, Zoology and Medicine.
In both of these examples, the list is accompanied by a general term that summarises what is being listed: main languages of South America in (a) and basic branches of Biology in (b). We might call these the “list names”. They are the same kind of generalization that is associated with example-giving (see 1. Simple Example-Giving), classification (see 162. The Language of Classification) and headings (see 178. How to Write a Heading). The list identifies what the list names mean (see 117. Saying More Precisely What is Meant).
The difference between (a) and (b) is the way the list is linked to the list name: with a verb in (a) and a colon in (b). Each of these presents its own problems.
1. Linking a List to a List Name with a Verb
Various link verbs are possible (see 162. The Language of Classification). Most obvious is are, and others include comprise (without of – see 42. Unnecessary Prepositions) and include (provided the list is only some of the possibilities indicated by the list name – see 1. Simple-Example-Giving and 96. Hedging 2). The following points are especially important about listing after a verb:
(I) Punctuation is unnecessary. It is tempting to use a colon or comma between a verb and a list because in speech there is often a pause there. However, not all spoken pauses need punctuation (see 91. Pronunciation in Reading Aloud). A much more reliable guideline is the general rule for colon use that is suggested in the post 17. Colons versus Semi-Colons: look to see whether the words before the list sound like a complete sentence by themselves; only if they do should a colon or other punctuation mark be used. List introductions ending with a verb are not usually able to stand alone as a complete sentence.
Some English writers do actually use a colon in such situations, but the necessity to do so can be disputed. I would suggest that the only exception to the complete-sentence rule might be when the list is physically separated from the words before it – as bullet points, for example (see 74. Sentence Lists 3: Bullet-Points), or in a table (see 104. Naming Data Sources with “As”).
(II) No additional list-introducing expressions like namely are possible. These expressions are possible only with some types of incidental listing (see 54. Sentence Lists 1: Incidental), and as a substitute for a colon (see below).
(III) You can start with either the list name or the list. The former is probably more common. This is because English generally prefers to put the main and the longest information of a sentence – both of which the list is here – at the end rather than the beginning.
(IV) Adding or omitting the before the list name creates different meanings. When the verb is BE, adding the (cf. the main languages of S. America above) says that the list covers all of the possibilities, while omitting the says that the list is not all of the possibilities – that it is only examples. Between the and the list name, a number word can be added to show how many items are in the list, but it is not compulsory.
2. Linking a List to a List Name with a Colon
A colon is common before a main-message sentence list when the preceding words make a possible complete sentence (as defined in the post 30. When to Write a Full Stop). The preceding words very often begin with there are (see 161. Special Uses of “There” Sentences). Check that the words before the colons in the following examples remain complete sentences with the lists removed.
(b) There are three basic branches of Biology: Botany, Zoology and Medicine.
(c) Biology has three basic branches: Botany, Zoology and Medicine.
Introductions like these are common before multi-sentence lists in English as well as single-sentence ones, but multi-sentence lists must follow a full stop, not a colon (see 122. Signpost Words in Multi-Sentence Lists).
The use of a colon between a possible complete sentence and a sentence-based list is much more characteristic of main-message sentence lists than incidental ones, where a comma is preferred (see 54. Sentence Lists 1). However, the difference between main-message and incidental lists is sometimes blurred. Consider this:
(d) Europe is the source of the two main languages of South America * Spanish and Portuguese.
Should the * here be replaced by a comma or a colon? In fact, either seems possible. The sentence can be primarily about the source of the listed languages, making the list incidental and the punctuation a comma; or primarily about the names of the languages, making the list central and the punctuation a colon. This possibility of alternative interpretations is perhaps due to the similarity of (e) to the following clear-cut example of incidental listing:
(e) The two main languages of South America, Spanish and Portuguese, originated in Europe.
The following further aspects of listing with a colon should be noted:
(I) The list name usually needs a number word before it (without the). The number word in (b) and (c) above is three. If you are not sure what the exact number is, you can use a vague number word like several, numerous, many, a number of or various (but not a lot of, which is too informal – see 108. Formal & Informal Words). You then confirm the incompleteness of the list by writing etc. or a synonym at the end.
Another solution is to combine an exact number word with a limiting word like basic, main, major or important (cf. three basic branches in [c] above) (see 96. Hedging 2: Lists and Predictions). You could also avoid having to use a number word altogether by introducing the list with a verb instead of a colon (see above, and also 162. The Language of Classification).
(II) There should be no list-introducing words after the colon. Expressions like namely, in other words, that is to say, viz or such as are no more possible after a colon than after a list-introducing verb. However, if a colon is possible, these expressions can be used instead of it, with a comma before them, not after (…languages, namely Spanish…). Note that such as is different from the others because it shows an incomplete list (i.e. one of examples – see 53. “As”, “Like” and “Such As” and 54. Sentence Lists 1); and you should avoid which are because, though logical, it is very rare in English.
(III) The list must end the sentence. If you want a sentence to continue after a colon-type list, you have to replace the colon with two commas or two dashes, like this:
(f) There are three basic branches of Biology – Botany, Zoology and Medicine – which are all popular with students.
PRACTICE EXERCISE (LIST PUNCTUATION)
Many of the points in this and the previous post about listing have involved punctuation. So here is an exercise that might help some of them to be remembered. You have to add necessary punctuation to each sentence (answers at the end).
1. There are four main German car manufacturers Volkswagen, Mercedes, BMW and Audi.
2. The English punctuation marks comprise full stops, commas, colons, semi-colons, dashes, hyphens, question marks, exclamation marks, quotation marks and apostrophes.
3. Every colour comprises one or more of the five fundamentals red, yellow, blue, black and white.
4. Engineering has three traditional branches mechanical, civil and electrical plus newer ones like aeronautical and electronic.
5. The two national languages of Canada English and French must be studied in all of the country’s secondary schools.
6. The most important ministers in Britain after the Prime Minister are the Chancellor of the Exchequer, the Foreign Secretary and the Home Secretary.
7. Four kinds of fuel power the majority of motor vehicles petrol, diesel, alcohol and electricity.
8. The two vertebrate classes mammals and birds are warm-blooded and have evolved comparatively recently.
1. Colon after manufacturers (the list ends a sentence with There are … ).
2. No additional punctuation (the list is introduced by a verb).
3. Comma or colon after fundamentals (the list ends at a full stop and follows a possible complete sentence lacking There are … ).
4. Two commas or two dashes around the list mechanical, civil and electrical (the words before are a possible sentence, but the list does not end the sentence).
5. Two commas around the list English and French (the list is an incidental one following a number word that gives the total of world possibilities).
6. No additional punctuation (the list is introduced by a verb).
7. Comma or colon after vehicles (the list ends at a full stop and follows a possible complete sentence lacking There are … ).
8. No punctuation (the list is an incidental one following the and a number word, and it does not name all of what the list name represents – unmentioned vertebrate classes are reptiles and amphibians).