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Commas, List, Including Oxford


A list consists of three or more grouped items: “bread and cheese” is a grocery list but not a grammatical list; “bread, cheese, and pickles” is both.

When constructing a list, place a comma between each item:

Variables analyzed in the regression included population size, GDP, third-party assistance, and number of previous endogenous conflicts.

That last comma—the one before the “and” (or “or”) that precedes the last item in a list—is known as the “Oxford” or “serial” comma. Ironically, perhaps, the Oxford comma is less frequently used in British English than American, and it is technically optional, provided you’re consistent within a given document.

 

Better safe than sorry

That said, leaving out the Oxford comma can potentially generate confusion (and chuckles) in your reader. Take, for example, this sentence:

This thesis is dedicated to my parents, Professor Chakrabarty and Professor Moustakas.

Did your parents advise your thesis?

The slip in meaning arises here because the comma is overworked: we could read this sentence either as a list with no serial comma or as apposition—a construction in which something is renamed. Compare this version, which clears things up:

This thesis is dedicated to my parents, Professor Chakrabarty, and Professor Moustakas.

Now it’s certain that we’re looking at a list.

Always including the Oxford comma is a useful way to minimize ambiguous list constructions and reserve that precious brainpower for other writing-related conundrums.

 

But wait

The Oxford comma is not a silver bullet for preventing ambiguity, however:

This thesis is dedicated to my kids, Sylvia, Hart, and Ezra, as well as my parents.

Are Sylvia, Hart, and Ezra the children here, or are they some other people this author wanted to thank? Again, are we looking at an appositive or a list?

In cases like this one, it can be useful to supplement commas with dashes or semicolons or other structural markers, which can clarify the boundaries between list items:

  • This thesis is dedicated to my kids—Sylvia, Hart, and Ezra—as well as my parents.
  • This thesis is dedicated to my kids; to Sylvia, Hart, and Ezra; and to my parents.

Finally, consider simply rearranging the list items:

I went on a walk with my dog, Lewis, and his sister.

Unless you’re packing multiple leashes and plenty of doggy bags, we’ll probably want this version:

I went on a walk with Lewis, his sister, and my dog

 

Lists vs. Nested Pairs

One particularly common comma error is treating a nested pair as a list:

Chapter I explains the research problem, methods, and discusses relevant literature.

This sentence is not a list; rather, it contains a pair of verbs (explains and discusses), one of which distributes to a pair of direct objects (research problem and methods). These pairs should each be treated in the usual way—connected with “and,” with no commas:

Chapter I explains the research problem and methods and discusses relevant literature.

In constructions like this one, writers might be tempted to retain the comma before the second "and": "explains the research problem and methods, and discusses relevant literature." But, for the same reason, this comma, too, is unnecessary.

 

Conclusion

As with any other construction, achieving clarity in your lists requires being attuned to possible misreadings and quashing them with punctuation, restructuring, and the rest of your syntactic toolkit.

 

List Commas Links

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All-Topics Index


The following index makes searching for a specific topic easier and links to the appropriate place in the sequenced material. We think we have most of them, but please email us at writingcenter@nps.edu if we are missing something!

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A

abbreviations

abstracts

academic writing

acronyms

active voice

apostrophes

argument

article usage

assignments, understanding them

audience

 

B

body paragraphs

brainstorming

building better sentences tips

 

C

citations

citation styles

clarity

clustering

coaching sessions, about

colons

commas, FANBOYS

commas, introductory

commas, list

commas, nonessential elements

commas, Oxford

commonly confused words 

compare-and-contrast papers 

concision

conclusions

conjunctive adverbs

coordinating conjunctions

copyright and fair use

critical thinking  

 

D

dangling modifiers

dashes

dependent marker words

double submission of coursework

drafting

 

E

edit your own work

editing – outside editors

exclamation points

executive summary

 

F

FANBOYS

FAQs

footnotes

free-writing

 

G

gerunds

grammar

group writing

 

H

hyphens

 

I

ibid.

introductions

 

J

Joining the Academic Conversation

 

L

LaTeX

library liaisons 

literature reviews 

logic and analysis 

 

M

memos

methodologies

 

N

note-taking

numbers

 

O

organization

outlining

Oxford comma

 

P

paragraph development 

parallelism

paraphrasing

parts of speech

passive voice

periods

persuasion

phrases and clauses

plagiarism, how to avoid through citations

plain language

polishing

prepositional phrases 

prepositions

pronouns

punctuation

purpose of research

 

Q

questions

quotation marks 

quoting

 

R

reading with intent

redundancies                                                                

reference software

reflection papers 

research

research questions

reverse outlining 

revising passive voice into active voice

revision

roadmaps                                            

run-on sentences 

 

S

self-citing

semi-colons

subjects, grammatical

significance

so-what?

spelling

standard essay structure

STEM/technical writing 

style

subject/verb agreement

 

T

technical writing

that vs. which

thesis writing

thesis advisors

thesis process overview

thesis process tips

thesis proposals – common elements                                                     

thesis statements

tone, professional

topic sentences 

transitions

types of papers

 

U

United States or U.S.?

 

V

verbs and verb tense

 

W

which vs. that

Why write?

writer’s block 

writing process