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Semicolons and Colons


A semicolon is not, as it turns out, half a colon; but, as their names imply, semicolons and colons are in some ways closely related—and quite distinct in others.

Both can be used to join independent clauses, with somewhat subtle distinctions in effect. Both are also involved in the construction of lists, though they play different—and complementary—roles.

 

Semicolons

  1. Semicolons can connect independent clauses; use of a semicolon indicates a close conceptual relation between discrete ideas:

Cras orchestrated Polyphème while captaining a torpedo boat during the Adriatic Campaign of WWI; it was to be his only opera.

Semicolons therefore overlap in function with coordinating conjunctions; the effect, however, is different:

Semicolons therefore overlap in function with coordinating conjunctions, but the effect is different.

Note that a semicolon (or colon) is required when joining two independent clauses without using a conjunction, even when a conjunctive adverb is present; joining independent clauses with a comma alone is an error called a comma splice:

Yes: The international system is, in the end, anarchic: there is no overriding authority capable of arbitrating conflicts between states.

No: The international system is, in the end, anarchic, there is no overriding authority capable of arbitrating conflicts between states.

Yes: The international system is, in the end, anarchic; however, institutions can incentivize cooperation among states.

No: The international system is, in the end, anarchic, however, institutions can incentivize cooperation among states.

Just remember: a comma splice willl not suffice.

(Opinions differ on whether it is acceptable to place a coordinating conjunction after a semicolon; so it’s up to you whether it’s worth risking stylistic censure in service of rhetorical effect.)
 

  1. When a list is made up of items that themselves contain commas, semicolons clarify the list structure:

U.S. capitol cities include Sacramento, California; Lansing, Michigan; and Carson City, Nevada.

Without the semicolons, the boundaries between list items are muddier:

U.S. capitol cities include Sacramento, California, Lansing, Michigan, and Carson City, Nevada.

 

  1. Semicolons separate multiple attributions in a single citation:

(Roussel 1912; Rimsky-Korsakov 1888)

 

Colons

The colon is a punctuation mark that says, in essence, “and here it is”: it announces that something just discussed is about to appear or be restated or further explained.

The relationship between the information on either side of the colon is therefore different from that created by a semicolon: while the semicolon indicates close relation, the colon generally signals identity.
 

  1. Like the semicolon, the colon can join independent clauses, indicating reiteration or further development of a given idea:

Launch conditions were far from ideal: high wind speeds sent the balloon off course by 15 km, thereby compromising data collection.

A semicolon here would be technically acceptable but less conceptually precise: the statement that follows the colon defines the aforementioned adverse conditions rather than introducing a separate but related idea. Compare this sentence:

Launch conditions were far from ideal; further trials were therefore necessary to collect the required data.

 

  1. Colons introduce lists, appositives (renaming / specification), and quotations:
  • The remainder of this thesis is organized as follows: Chapter II provides . . . ; Chapter III describes . . . ; Chapter IV . . . .
  • In this case, however, one instrument of national power overshadows the others: economics.
  • Sun Tzu said it best: "Don't believe everything you read on the internet."

When using the colon in this way, be sure the introductory statement is a complete independent clause; that is, do not insert a colon where it will create an incomplete clause:

Yes: The DIME paradigm comprises diplomacy, information, military, and economics.

No: The DIME paradigm comprises: diplomacy, information, military, and economics.

Here, “comprises” needs an object(s), so cutting off the syntax with a colon separates sentence components that need to be grouped together in the clause.

 

  1. Finally, colons perform assorted functions in constructions related to time, mathematics, and citation styles.

 

More Information on Semicolons and Colons

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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