Guide to the
Marking of Written Assignments
by Ian Johnston
[This document is in the public domain and may be used, in whole or in part, by anyone. Released July 2000]
SECTION 5: PARALLELISM OR PARALLEL STRUCTURE
5.1 The term parallelism or parallel structure refers to a style in which items with a similar function in a sentence have, as much as possible, the form of a list of similar items. This definition is not very helpful perhaps, but a few examples in the sections below will make the concept sufficiently clear.
The simplest form of parallel structure is a simple list of nouns, as follows:
She purchased a pen, a book, three pencils, and a ruler.
Here there is a list of items which the subject purchased. All the items are nouns (pen, book, pencils, and ruler), and commas separate the items in the list. A parallel list may have only two items, in which case there is no comma between them: e.g., She purchased a book and a pen.
5.2 Be careful that in a simple list the items do not slip out of parallel, that is, that one or more of the items does not have the same form as the other items.
She was a good student, a championship athlete, and as a friend she was loyal.
The sense of the above sentence is clear, but to maintain the parallelism the three items should be the same in form. Thus, you should rewrite the sentence so that the third item has the same form as the previous two.
She was a good student, a championship athlete, and a loyal friend.
5.3 Parallelism commonly goes astray in a list of only two items, in which the second item has a different form from the first. Notice the following example:
He explained the operation of the computer and how much it cost.
In this example, the first item in the list is a noun (the operation), and the second is a dependent clause (how much it cost). To keep the parallelism exact, rewrite the sentence so that both items have the same form. Notice the two possibilities:
explained the operation and the cost of the computer.
He explained how the computer worked and how much it cost.
Here is a similar example:
The supervisor asked that she measure the samples and to enter the results in the computer.
Here again there are two items in the list (the two things the supervisor asked). The first is a subordinate clause (that she measure the samples) and the second is an infinitive construction (to enter the results in a computer). Rewrite the sentence so as to keep both items the same in form.
The supervisor asked her to measure the samples and to enter the results in the computer.
The supervisor asked that she measure the samples and that she enter the results in a computer.
Notice that in these two examples there is no comma separating the items in the list. If you are uncertain why this is correct, see 1.30 above.
5.4 Parallelism should also govern the structure of a sentence in which there are two or more similar dependent clauses or phrases.
Since the leader is ill and since the weather is bad, we will return today.
Notice that the two dependent clauses (both giving reasons) come one after the other in parallel (i.e., with the same structure). You could, of course, omit the and since, so that there is only one dependent clause. Either structure is much better than one which splits the two dependent clauses, placing one before and one after the main clause (e.g., Since the leader is ill, we will return home, since the weather is bad).
5.5 In formal and technical writing, parallelism is particularly important when you are writing a vertical list of items (whether numbered or not). Keep each item in the list the same in form as each of the others. If the items are lengthy, make each one a complete sentence.
At the end of each item in a vertical list, follow the appropriate punctuation, as if the list was horizontal (i.e., in your own sentence). If the items in the list are each complete clauses, then put a full stop or a semi-colon at the end of each item. If the items in the list are each phrases or simple nouns, then put a comma at the end of each one, and a full stop at the end of the last item (see 5.8 below).
5.6 If you are presenting a list of definitions (for example, in a glossary at the start of a report), then make sure each definition has the same structure as each of the others (usually a complete sentence for each one).
5.7 Parallel structure is particularly important when you are reporting what someone else said. If the parallelism is not clear, the reader may get confused about what information is reported and what is your own idea. Note the following sentence:
The report states that Fords used to be more reliable than Chevrolets but recent road tests have cast doubt on this opinion.
In this sentence, there might be some confusion whether the second idea (about the recent road tests) comes from the report or from the opinion of the writer of the sentence (i.e., you). To clarify that this second statement is also part of the report, make the parallelism clear by repeating the word that, as follows:
The report states that Fords used to be more reliable than Chevrolets but that recent road tests have cast doubt on this opinion.
This structure clearly indicates that the second opinion is also part of the report you are referring to. If the second point is not from the report, then make that clear by starting a new sentence.
The report states that Fords used to be more reliable than Chevrolets. But recent tests have cast doubt on this opinion.
When you are passing on information from some other source, repeat the that at the introduction to each part of the reported material (as in the above example). Notice the following example:
He told us that he was in charge, that we had chosen him, and that he would not hold another election.
5.8 Parallel structure also applies to a numbered list, whether the list is within your own sentence or set in a column by itself. Note the following examples.
The three main causes of the revolution were (1) the economic crisis, (2) the negligence of the government, and (3) the urban riots.
We will need the new equipment for the following reasons:
(1) our present engine is in very poor condition;
(2) our productivity is declining;
(3) present methods are producing too much butt shatter.
5.9 When you write a list in a vertical column (as in the second example in 5.8 above), you normally omit the and between the last two items.
5.10 Notice the punctuation and the use of brackets in the above list in 5.8. Do not use full stops at the end of each item in a vertical list, unless each item is a complete sentence (full stops would be all right in that example in 5.8 because each item is a complete sentence). Put a full stop after the last item.
5.11 In a vertical list, the writer should normally indent the margin of the list, indicate the start of each item (usually with a number or a letter of the alphabet), and keep the vertical margin straight, so that the reader can see the list clearly. Do not write a list so that the second line of a particular entry in the list goes back to the margin of the main text. Set the margin for the list with the first letter of the first word in each item. If you are working with a word processor, use the numbering function from the format menu. That will format the list in accordance with the above instructions. Notice the following example.
We have a number of recommendations to make as a result of this investigation.
The company should immediately recall all the connector pins in the batch manufactured in the first week of October 1990.
The purchasing agent must contact the manufacturer (Acme Industries) as soon as possible to inform them in writing of the defective connectors.
Until such time as Acme Industries indicates a greater commitment to quality control, we should be very careful about ordering routine supplies from them.
Notice in this list how the margin is slightly indented, the numbers line up vertically, and the items in the list all have the same left-hand margin. Since each item in this list is a complete sentence, it starts with a capital letter and ends with a full stop. The numbers could be in brackets, but, if so, then there would be no full stop after them: (1) or 1. But not (1.) or 1.) or 1).
5.12 Always start a vertical list on a fresh line. Do not put the first item on the same line as the sentence which introduces the list. See the example in 5.11 above.
5.13 Do not use capital letters at the start of each item in a vertical list, unless that item is a complete sentence or requires a capital letter for some special reason (e.g., a brand or company name). If each item in the vertical list is a complete sentence, then you should use capital letters at the start of each item and a full stop at the end (as in the example in 5.11 above).
5.14 If you use the expressions firstly, secondly, thirdly or in the first place, in the second place, in the third place, or first, second, third, then punctuate them with commas. And be consistent. Do not switch from one set to another in the middle of a list.
First, we measured the ground. Second, we divided up the different tasks. And, third, we ordered supplies.
Notice the punctuation in the above example.
5.15 Be particularly careful whenever you use the parallel co-ordinators (either . . . or, neither . . . nor, both . . . and, not only . . . but also). These expressions always co-ordinate two items in parallel. Make sure that each co-ordinator comes immediately in front of one of the items being coordinated. The problem here is that the first co-ordinator often comes in too early. Notice the following sentence:
She not only purchased the books but also the pens.
Notice in the above example that the two items in question are books and pens. The first co-ordinator, however, is out of place. It must come immediately before the first item in the pair of things being coordinated. Rewrite the sentence as follows:
She purchased not only the books but also the pens.
Take special care with either. That word almost invariably comes in the wrong place.
She either quits or I do.
Two independent ideas are being coordinated here. Place the either at the very start of the first option. Notice the commas between the items here because each is an independent clause.
Either she quits, or I do.
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