Semicolons. Although the semicolon is used in more limited and straightforward ways than the comma is, the semicolon is frequently misused by authors of all kinds. The pause it indicates is stronger or longer than the pause specified by a comma, but weaker than that indicated by a full stop (for the latter, see Section 5.6.2), and its effect is somewhat different from that of the colon, but the semicolon nonetheless tends to be used incorrectly in situations when one of those three types of punctuation would be more appropriate, much as a comma, stop or colon is sometimes used when a semicolon would be better. In most situations, a semicolon resembles a full stop in function: its most common use is to provide punctuation between two independent clauses that are not joined by a conjunction and could, were they separated by a full stop instead, form two sentences. However, the semicolon generally implies a closer relationship between the two clauses than a full stop might: ‘Sally wanted to rake the leaves Sunday morning; an unexpected snowfall Saturday night prevented her from doing so.’ A colon should not be used instead of a semicolon between such clauses unless the second clause specifically explains, illustrates or provides examples of what is asserted in the first clause (see the discussion of colons below). A semicolon can also be used instead of a comma between two main clauses (whether they feature different subjects or share the same subject) that are joined by a conjunction and already make use of internal commas, in which case the semicolon indicates a stronger division than the commas and clarifies the sentence structure: ‘Richard was planning to buy a new computer, television and mobile phone at the electronics shop and then stop at the grocery store, where he intended to fill the gas tank as well; but the electronics shop was sold out of all the products he wanted and the line for gas was very long, so he arrived home with groceries only.’

A semicolon is also required when two main clauses are linked not by a conjunction but by an adverb such as ‘indeed,’ ‘however,’ ‘therefore’ or ‘nevertheless’ or by an adverbial phrase. In these situations, the semicolon should appear before the adverb or adverbial phrase: for example, ‘Sally wanted to rake the leaves Sunday morning; however, an unexpected snowfall Saturday night prevented her from doing so’ and ‘The instructor intimidated him; as a result, he dropped the course.’ Semicolons are also used to intensify the divisions and clarify the relationships between the items in a series or list in which the individual items are complex and already contain commas and/or other punctuation: ‘She explained, in support of her husband, that he had been experiencing recent difficulties, including crashing their only car; that he had lost his job and had not been able to find a new one, although he had been searching every day; that he had never behaved in this way before, at least as far as she knew; and, finally, that he had already removed the snow from his neighbour’s car, offering a sincere apology after he finished.’ Semicolons are often used when listing the copyright holders of material used in a thesis – ‘I am grateful for permission to reproduce images of manuscripts from the collections belonging to the Bodleian Library, Oxford; the British Library, London; and the Worcester Cathedral Library.’ Semicolons are also used to separate individual in-text references in an author–date system of referencing when two or more references are gathered in a single set of parentheses – ‘(Brentwood, 2010; Chang, 2006; Kovak, 1990; Olsen, 2013)’ – and they can be used in a similar way in a note system of referencing when more than one reference (whether complete or shortened) is included in a single note, as they are in this footnote.[1] In the full bibliographical references that appear in reference lists or notes, a semicolon is used in some styles between the name of the publisher and the date of publication, and occasionally in other positions as well (for more information on using punctuation in references, see Chapter 7). 

[1] Hilmo, “Power of Images,” 158; Kerby-Fulton, “Professional Readers,” 223; Olson, “Romancing the Book,” 102.

When trying to avoid a numeral or symbol that would be awkward at the beginning of a sentence, you can use a semicolon instead of a full stop before the numeral or symbol: for example, ‘Although I approached an equal number of instructors and students, more students than instructors responded positively. 137 students agreed to take part in the study, but only 56 instructors wished to participate’ requires rewording to avoid ‘137’ at the opening of the second sentence, but writing the numeral out in words to correct the problem would be somewhat awkward, especially since ‘56’ would be best written out as well (on using and formatting numbers, see Section 6.4). By using a semicolon instead of the full stop, the problem is resolved: ‘Although I approached an equal number of instructors and students, more students than instructors responded positively; 137 students agreed to take part in the study, but only 56 instructors wished to participate.’ Because the information after the semicolon in this example provides explanatory details about what has come before it, a colon would be a viable alternative to the semicolon (see below).

Colons. The functions of the colon are, like those of the semicolon, well defined and straightforward, yet it, too, is often misused, even by scholarly authors. As a general rule, a colon should not be used as a substitute for a semicolon, comma or full stop because its significance is different. As New Hart’s Rules puts it, using a colon in the process, a ‘colon points forward: from a premise to a conclusion, from a cause to an effect, from an introduction to a main point, from a general statement to an example’ (Ritter, 2005, Section 4.5). Functioning much as the words ‘for instance,’ ‘for example,’ ‘namely,’ ‘because,’ ‘that is’ and others do, a colon introduces an explanation, example, description, elaboration or illustration of what has appeared before it. ‘There was so much food that three of the dishes brought to the potluck were not even touched: the bean salad, the largest pan of lasagne and the lemon cake’ uses a colon correctly and, like the quotation from New Hart’s Rules I have used above, also demonstrates how the text following a colon need not contain a verb or be able to stand on its own as a sentence or independent clause. A colon can be used instead of a semicolon, however, between two independent or main clauses, but only when the second clause specifically explains, illustrates or otherwise elaborates on what has been said in the first: for example, ‘We were delighted, but especially those who had worked so hard to achieve this goal: one of the younger members even shouted out with glee’ and ‘Although I approached an equal number of instructors and students, more students than instructors responded positively: 137 students agreed to take part in the study, but only 56 instructors wished to participate.’

One of the primary functions of the colon is to introduce a list or series of items – ‘Three of the dishes brought to the potluck were not even touched: the bean salad, the largest pan of lasagne and the lemon cake’ – and is frequently used for this purpose after the words ‘as follows’ or ‘the following’: ‘The following dishes were not eaten: the bean salad, the largest pan of lasagne and the lemon cake’ (see Section 5.5.2 above for more information on using colons with lists). A colon should not be used, however, before a list or statement that is introduced by a verb or a preposition in such a way that the list or statement correctly completes the sentence begun by the introductory words without the need to use a colon: ‘The dishes that were not eaten included the bean salad, the largest pan of lasagne and the lemon cake.’

A colon is sometimes used instead of a full stop before a series of related sentences that illustrate or provide examples of what has been mentioned in the preceding sentence, as in the following example.

A number of problems arise when a doctoral student does not prepare carefully for the thesis examination: For one, his or her presentation may be inadequate or disorganised and give a bad impression. Second, the thesis may be riddled with errors that could easily have been corrected through careful proofreading. Third, the candidate may not be able to answer in intelligent ways the questions posed by the examiners. Finally, if the problems are drawn to the student’s attention, he or she may become flustered or angry and make matters worse.

I have used an initial capital immediately after the colon in this example, primarily to demonstrate how a full sentence follows a colon, but this would be an appropriate format for American English, in which a colon is followed by a capital if it introduces a grammatically complete sentence. In running text in British English, however, the word following a colon is usually not capitalised (unless it is a proper noun), so ‘For one’ in the above example would probably be ‘for one’ in British English; everything else would remain the same.

When introducing direct speech, a colon can be used, as it often is between the name or term identifying a speaker and the transcription of his or her words when recording the dialogue from interviews:

INTERVIEWER: Did you find the items on the questionnaire difficult to understand?

PARTICIPANT A: No, most of them seemed clear to me.

INTERVIEWER: Can you remember which ones did not?

Here, the words following the colons should bear an initial capital to mark the beginning of the direct speech regardless of whether British or American English is used. A capital letter can also follow a colon that is used to introduce a quotation or extract – ‘J.R.R. Tolkien’s Hobbit begins with a line that the author apparently scribbled on a student paper he was grading: “In a hole in the ground there lived a hobbit”’ – with the capital being most likely if the quotation begins with a full sentence or continues for more than one sentence (for more information on quotations and the punctuation associated with them, see Chapter 8 below). It is essential to ensure that whatever format is chosen for capitalisation in such cases is used consistently for identical or similar situations throughout a thesis.

Particularly in American English, a colon is used at the beginning of a formal speech, letter or other communication immediately after the mention of those addressed – as in ‘Ladies and Gentlemen:’ or ‘Dear Editor:’ – but a comma is usually used for the same purpose in British English. Colons often appear in titles as well, primarily between a main title and a subtitle to introduce the latter, as the colon does in the title of this book: PhD Success: How To Write a Doctoral Thesis. If a proper noun follows the colon in such titles, it should bear an initial capital; otherwise, the colon can be followed by either an uppercase or lowercase letter, depending on the guidelines you are following and your usual practice regarding the format of titles and headings, with consistency being a primary goal (for more information on headings and capitalisation, see Sections 6.1 and 6.2.1). Paragraph headings, particularly in abstracts, are sometimes followed by a colon that functions in an introductory way, and if the heading is in a special font, the colon often is as well: ‘Objectives: The two primary objectives of this research were.’ A colon can also be used with or without spaces around it in ratios (e.g., ‘a ratio of 2:1’) and without spaces in chapter and verse references to the Bible (Genesis 2:4) and in URLs (the PRS web site at http://www.proof-reading-service.com/). Finally, colons are used to punctuate full bibliographical references in reference lists: depending on the style and system of referencing, a colon can appear between the place of publication and the publisher, after ‘in’ or ‘In’ when referring to a chapter in a book and before issue and page numbers when citing journal articles (see Chapter 7 for further information on punctuation in references).

A dash (en rule or em rule) can be used instead of a colon in some situations, such as when introducing a brief explanation or example of what has gone before or a brief list or quotation: for example, ‘Three of the dishes remained untouched – the bean salad, the largest lasagne and the lemon cake.’ However, a dash is more informal than a colon and tends to imply an aside or afterthought rather than a main idea (see Section 5.6.4 below), so it is not really interchangeable with a colon, and a colon should be used in most cases. Whether a colon or a dash is employed, only one of them should be used, not both. It was once common practice to use a colon followed by a dash (:–) to introduce a list or other displayed material such as a block quotation, but this is no longer the case, so only if you are quoting an earlier source should this construction be retained.