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Essential Concepts

Punctuation

• End punctuation marks (periods, question marks, and exclamation points) indicate the sentence type and tone. Use periods for statements, question marks for direct questions, and exclamation points to express strong emotion or emphasis—while avoiding overuse, especially in formal writing. If a question is implied rather than asked directly, it ends with a period (e.g., She asked where the bus was).
• Punctuation clusters—like multiple ending marks—should be avoided. Use only one terminal punctuation mark per sentence. When punctuation meets abbreviations or parentheses, follow conventions for clarity and consistency.
• Hyphens join words that function together as a single idea—such as compound adjectives (high-speed chase), “self” words (self-aware), or to prevent ambiguity (re-sign vs. resign)—but are generally not used with -ly adverbs or familiar word pairs unless clarity requires it (e.g., well-known before a noun, but well known after).
• Dashes come in two forms: em dashes and en dashes. Em dashes create emphasis or insert commentary, while en dashes show ranges (e.g., June–August) or relationships (New York–Boston train).
• Parentheses add supplementary information or clarification. The sentence should still make sense without the parentheses. Follow punctuation rules depending on whether the parenthetical statement is a full sentence or part of one.
• Brackets are used to add clarification or indicate changes within quoted material. Use [sic] to highlight errors in a source, and use brackets to insert explanatory terms or names within a quote.
• Ellipses indicate omitted material in a quote but do not replace original punctuation. Use them to shorten quotes while retaining the original meaning, and preserve periods or commas if they occur near the ellipsis.

Apostrophes and Quotation Marks

• Apostrophes can be used to show possession. Use apostrophe + s to indicate ownership (the student’s paper) and just an apostrophe for plural possessives ending in s (the teachers’ lounge). Avoid using apostrophes to make regular plurals. Tip: If you can rephrase the phrase using of (e.g., the book of the teacher), then possession is indicated, and an apostrophe is appropriate.
• Contractions use apostrophes to replace omitted letters. Common examples include don’t (do not), it’s (it is), and you’re (you are). Be careful not to confuse contractions with possessive pronouns like its, your, or their, which do not take apostrophes.
• Use quotation marks for direct quotes, speech, and short works. Enclose exact wording from a source in quotation marks and include a citation. Don’t use quotation marks for paraphrased ideas, but still cite the source. Quotation marks are also used for dialogue, titles of short works (like poems or songs), and occasionally for emphasis—though italics are preferred for emphasis in academic writing.
• Quotation mark rules include punctuation placement and nested quotes. In American English, periods and commas always go inside quotation marks, while other punctuation marks (like colons and question marks) depend on whether they’re part of the quoted material. Use single quotation marks for a quote within a quote: He said, “She called it ‘a disaster.’”
  

Commas

• Use commas to set off transition words and phrases—such as however, therefore, and nevertheless—especially when they appear at the beginning, middle, or end of a sentence. If the transition connects two independent clauses, it must follow a semicolon or period.
• Set off nonessential descriptive phrases and introductory elements with commas. If the added detail or introductory phrase can be removed without changing the core meaning of the sentence, it should be enclosed in commas (e.g., “Because it was raining, we stayed inside” or “My sister, who is a musician, loves jazz”).
• Use commas in dates and locations, separating the day from the year and the city from the state or country (e.g., July 4, 1968, in Cleveland, Ohio).
• Place a comma before a coordinating conjunction (FANBOYS)—for, and, nor, but, or, yet, so—only when it joins two independent clauses (e.g., I was late, but I still made the meeting).
• Use commas to separate items in a list, and consider using the serial (Oxford) comma before the final item to improve clarity, especially in complex or potentially ambiguous lists.
• Avoid incorrect comma placement: Don’t insert commas between a subject and its verb, between compound subjects or verbs, before or after conjunctions (unless joining independent clauses), or directly before a preposition—such placements disrupt sentence flow and clarity.

Semicolons and Colons

• Use semicolons to connect related independent clauses without a conjunction, or before transitional phrases like however or at the same time when what follows is also a complete sentence.
• Avoid semicolons before dependent clauses—if the second idea can’t stand alone as a sentence, use a comma instead (or no punctuation if the phrase follows the main clause).
• Semicolons clarify complex lists, especially when list items include internal commas (e.g., “São Paulo, Brazil; Kobe, Japan”).
• Colons introduce or emphasize what follows, including explanations, summaries, or quotations—as long as the preceding clause is a complete sentence.
• Colons can also introduce lists, but only after a full sentence. Avoid using a colon after phrases like “such as” or “including,” or after incomplete statements.

Complete Sentences

• A sentence fragment is an incomplete sentence that lacks a subject, a verb, or a complete thought. To be complete, a sentence must meet all three criteria. Some fragments are created by dependent clauses (e.g., starting with “which” or “because”) that can’t stand alone. These should be revised to include an independent clause. Fragments can occur even in long sentences, and short sentences can be complete; length does not determine completeness—grammar and meaning do.
• Run-on sentences improperly join two or more independent clauses without the necessary punctuation or conjunction. This includes fused sentences (two sentences joined with no punctuation) and comma splices (two sentences joined with just a comma). 
• To fix a run-on or comma splice, you can:
  • Use a period to create two sentences.
  • Use a semicolon if the ideas are closely related.
  • Use a comma and coordinating conjunction (FANBOYS).
  • Use a colon when the second clause explains or expands on the first.
  • Rewrite the sentence to eliminate the issue.
• Adverbial conjunctions like “however” or “therefore” are not substitutes for FANBOYS and require proper punctuation—typically a semicolon before and a comma after.

Glossary

brackets [ ]

punctuation marks that are used within quoted text to add clarification or indicate an error in the original source (marked with [sic]). They show that the inserted material is not part of the original quotation

colon ( : )

a punctuation mark that signals that what follows elaborates, explains, summarizes, or lists something introduced before it. It creates a strong pause that links closely related ideas

contraction

a shortened form of a word or group of words, created by replacing omitted letters with an apostrophe (e.g., don’t for do not, he’ll for he will)

descriptive phrases

phrases that provide additional, nonessential information about a noun and are typically set off with commas. If the phrase can be removed without altering the core meaning of the sentence, it should be separated by commas

ellipsis ( … )

punctuation marks that indicate the omission of words in a quotation or a pause in thought. They consist of three spaced periods and retain any original punctuation before or after them

em dash ( — )

a punctuation mark used to emphasize or set off information, often replacing commas, parentheses, or colons for a stronger impact or interruption

en dash ( – )

a punctuation mark used to represent ranges in time, dates, or numbers, and can also indicate connections such as routes or relationships

end punctuation

marks used to signal the end of a sentence; the three primary types are the period, question mark, and exclamation point

exclamation point ( ! )

used to express strong emotion, surprise, or emphasis; typically avoided in formal writing

hyphens ( – )

punctuation marks that are used to join words or parts of words, typically to clarify meaning, form compound terms, or prevent confusion in multi-word modifiers

parentheses ( )

punctuation marks that are used in pairs to enclose extra information or explanations that are helpful but not essential to the main sentence

period ( . )

used to end declarative sentences or statements that are not questions or exclamations

plural possessive

a plural possessive shows ownership by more than one noun. If the plural noun does not end in s, add ’s; if it does end in s, add only an apostrophe (’) after the final s

prefix

a letter or group of letters added to the beginning of a word to change its meaning; most prefixes do not require hyphenation unless added to a proper noun or needed to avoid ambiguity

question mark ( ? )

used to end direct questions; not used with indirect questions

quotation marks (” “)

punctuation marks that are used to enclose exact words taken from another source, typically for direct quotations in academic writing. They signal that the words inside are not the writer’s own

run-on sentence

when two or more independent clauses are joined incorrectly, either with no punctuation or only a comma without a coordinating conjunction

scare quotes

quotation marks that are used around a word or phrase to signal irony, doubt, or that the term is being used in a non-literal, non-standard, or questionable way

semicolon ( ; )

a punctuation mark that connects two independent clauses that are closely related in meaning, or separates complex items in a list

sentence fragment

an incomplete sentence that lacks a subject, a verb, or does not express a complete thought. It cannot stand alone as a grammatically correct sentence

serial comma (Oxford comma)

the comma placed before the final conjunction in a list of three or more items (e.g., “apples, oranges, and bananas”). While required by MLA, APA, and Chicago style guides, AP style omits it. Use of the serial comma can help prevent ambiguity in complex lists

single quotation marks (‘ ’)

punctuation marks that are used to indicate a quotation within another quotation

singular possessive

a singular possessive shows ownership by a single noun and is formed by adding an apostrophe followed by s (’s) to the end of the word, even if the word already ends in s

suffix

a letter or group of letters added to the end of a word to form a new word or alter its function; hyphens are generally unnecessary unless needed to clarify pronunciation or meaning

transition words

words or phrases (e.g., however, therefore, in addition) that connect ideas and show relationships between them, such as cause and effect, contrast, or sequence

word blend

a compound formed by merging parts of two or more words into one new term, often used without hyphens when the meaning is clear and widely accepted