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Quick Punctuation Guide
Comma

Use
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•
before a coordinating conjunction linking main clauses
following introductory clauses and phrases
between items in a series
to set off incidental comments (appositives,
nonrestrictive clauses)
when meaning is unclear without its use
when authority figures tell you to use one while you
are writing for them

Don't use
• a single comma between a subject and its
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verb
when a subordinate clause follows a main
clause
before the first or after the last item in a series
between two words joined by a coordinating
conjunction
Semicolon

Use
• instead of a coordinating conjunction between
•

main clauses
to separate main groups of items in a list
already using commas
Don't use
• too frequently in the same document
• between parts of unequal grammatical rank
Colon

Use
• to connect explanation, details, or a quotation
to a main clause

Don't use
• more than one in a sentence
• directly after prepositions or verbs unless you
knowingly choose to violate the normal usage
rules
Dash

Use

Don't use
• to indicate a sudden change of tone or idea
• to emphasize, clarify, or interject
• too often
• a hyphen(-) for a dash; dash(--) = two
consecutive hyphens or an em-dash
Parentheses

Use

Don't use
• to insert nonessential material
• to indicate citation
• to introduce acronyms, abbreviations, etc.
• if the material can be better incorporated
another way
Brackets

Use
• to interpolate in quotations
• as parentheses inside parentheses
Ellipsis

Use

Don't use
• to indicate an omission
•
•
to indicate that you're starting a sentence in
the middle
to alter meaning in a quotation
Apostrophe

Use
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•

to indicate possessive case for nouns and indefinite
pronouns
to indicate omissions in contractions
to indicate plurals of odd words, acronyms, and
numerals (opt.)
Don't use
•
•
to indicate possessive case for personal pronouns
to add an "s" for making standard words plural
Single Quotation Marks

Use
• within double quotation marks or for unusual
terms

Don't use
• to pretend you're not really using a word
you're using
Double Quotation Marks


Use
•
•
•
to enclose direct quotes
for minor (internal) titles
correctly with other marks:
• place period and comma inside
• place colon and semicolon outside
• place question mark and exclamation point inside when
they apply only to the quoted matter, and
• outside when they apply to the whole sentence
Don't use
•
to pretend you're not really using a cliche you're using
Hyphens

Use *
• to integrate words into a functional unit
• when your keyboard lacks bullets to set off
listed items
Prepositional Phrases

Prepositions connect nouns or pronouns to
other words.
•
The phrases created by this linkage are called
prepositional phrases, and they usually function as
modifiers— adjectives or adverbs—adding detail to
the sentence.
• Tree frogs are colorful.
• Tree frogs of the Colombian mountain ranges to the
north of the country's capital near the border are colorful,
with markings on their limbs, between their eyes,
underneath their arms, and on their backs in hues of
red, orange, green, purple, and black.

Prepositional phrases consist of a
preposition, which can be a word or a phrase,
and its object:
•
Prepositions Objects
• according to Aristotle
• because of jellyfishes' sensitivity
• since the beginning
• with regard to ecological studies
• with the exception of white whales
• throughout the article
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Lists of prepositions can be found in any grammar book :
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above,
around,
across,
below,
between,
by,
over,
past,
since,
throughout,
concerning,
despite,
etc.

Technical writers tend to use prepositions frequently
because they often need to communicate details:
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describing specific features of animals,
analyzing the particular configurations of chemicals,
explaining the effects of procedures, and
the like.
However, overuse of prepositional phrases confuses,
rather than clarifying, the writer's point.
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The design of the apparatus with the tubing and the electrical
wiring was useful for diagnosis of the transmission of electrical
impulses in the nerve tested.
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Revising to avoid overuse of prepositional
phrases makes the ideas and information
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more readable,
easier to understand, and
easier to retain.
Consider using the object of the preposition as
an adjective or converting the idea into a
subordinate clause.