Tips for More Effective Technical Writing

Tip #15 Commas & Lists

COMMAS

Comma Use in a Series or List

When you have 3 or more words (phrases or clauses) in a series with no other punctuation inside the series, separate the individual elements with commas [ , ]. Always use a comma before the conjunction (and, but, …) before the last ITEM.

GUIDELINE FOR USING COMMAS IN A SERIES
"21.2.2 Series
"In a series consisting of three or more words, phrases, or clauses with no internal punctuation of their own, separate the elements with commas. Always use a comma before the conjunction that introduces the last item."
Source: Turbian, Kate L. A Manual for Writers of Research Papers, Theses, and Dissertations. Revised by Booth, Wayne C. et. al. Chicago: The University of Chicago Press, 2007. See also The Chicago Manual of Style 16th ed., 2010, p. 312.

Comma Use in a Series or List

Used, but Possibly Confusing BETTER

heart, lungs, kidney, liver and brain
… in London, Hanoi, Berlin and Cairo.


Jones, James and Smith attended the conference.


Attending the conference were Jones, James and Smith.

heart, lungs, kidney, liver, and brain
… in London, Hanoi, Berlin, and Cairo.


Jones, James, and Smith attended the conference.


Attending the conference were Jones, James, and Smith.

Semicolon Use in a Series or List

The semicolon [ ; ] indicates a greater break in the continuity of a sentence than a comma does. Use semicolons to separate the items in a series when one or more of the items includes a comma.

Confusing BETTER
… in London, United Kingdom, Hanoi, Vietnam, Berlin, Germany, and Cairo, Egypt.

Green indicates vegetation that remained stable, red, vegetation that disappeared, yellow, new vegetation.
… in London, United Kingdom; Hanoi, Vietnam; Berlin, Germany; and Cairo, Egypt.

Green indicates vegetation that remained stable; red, vegetation that disappeared; and yellow, new vegetation.

The semicolon [ ; ] is also used when the clauses are long and complex, and have commas or other punctuation in them.

Used, but Confusing BETTER
Although productivity per capita in US industry is much more than that in China, China has an increasingly well educated young labor force, but the crucial point is that knowledge, which is transferable between peoples, has become the most important world economic resource. Although productivity per capita in US industry is much more than that in China, China has an increasingly well educated young labor force; but the crucial point is that knowledge, which is transferable between peoples, has become the most important world economic resource.

Although productivity per capita in US industry is much more than that in China, China has an increasingly well educated young labor force; but the crucial point is that knowledgewhich is transferable between peopleshas become the most important world economic resource.

Use a semicolon before then, however, thus, hence, indeed, accordingly, therefore, and other conjunctive adverbs (接続副詞) when those words are used as a transition between two independent clauses.

Comma Misuse GOOD 1 (minimal standard grammar)
Some think that freedom always comes with democracy, however, many voters in many countries have voted for governments that they know will restrict their rights. → Some think that freedom always comes with democracy. However, many voters in many countries have voted for governments that they know will restrict their rights.
GOOD 2 (more advanced, complex grammar)
Some think that freedom always comes with democracy; however, many voters in many countries have voted for governments that they know will restrict their rights.

LISTS

Acceptable BETTER
AMCAP's strategy to achieve its objectives was through reforestation and watershed management interventions, the introduction of improved agro-technology for upland farming, rehabilitation of irrigation facilities, small-size livestock improvement, and building of local capacity for improved rice seed multiplication. AMCAP's strategy to achieve its objectives was through (1) reforestation and watershed management interventions, (2) introduction of improved agro-technology for upland farming, (3) rehabilitation of irrigation facilities, (4) small-size livestock improvement, and (5) building of local capacity for improved rice seed multiplication.
in-text lists
Use Arabic numbers in parentheses [ ( ) ];
leave 1 space before, and one space after.
AMP's strategy to achieve its objectives was through …
  1. reforestation and watershed management interventions,
  2. introduction of improved agro-technology for upland farming,
  3. rehabilitation of irrigation facilities,
  4. small-size livestock improvement, and
  5. building of local capacity for improved rice seed multiplication.
Vertical lists
Use when (1) the list is long[er], or (2) you want to give the list greater emphasis.
Indentation from left margin is necessary.

Acceptable BETTER
The thesis committee gave three reasons for not awarding a doctoral degree: insufficient originality, inadequate method, and improper data interpretation. The thesis committee gave three reasons for not awarding a doctoral degree: (1) insufficient originality, (2) inadequate method, and (3) improper data interpretation.
in-text lists
If you are already using Arabic numbers for another purpose, substitute lowercase letters for the numbers.
The thesis committee gave three reasons for not awarding a doctoral degree: (a) insufficient originality, (b) inadequate method, and (c) improper data interpretation.
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