A Comprehensive Guide To Punctuation

Types of punctuation marks

  • Periods, question, and exclamation marks
  • Commas, colons, and semicolon 
  • Hyphens and dashes
  • Quotation marks and ellipses
  • Brackets, braces, and parentheses
  • A discussion of each mark follows, in alphabetical order by name of mark. Also includes how to divide words; use of numerals/numbers; possessives; and common errors in punctuation. 

    Apostrophe (‘) is used to indicate possession, contractions, and plurals. 


    • The possessive form of singular nouns ends in ‘s, including nouns ending in s, x, z, ch, or sh. For example: a dog’s life, a lass’s smile. 
    • The apostrophe follows the s for the possessive of plural nouns except for plurals which do not end in s. For example, you would write: zebras’ stripes, but children’s books. 
    • No apostrophe is used for personal pronouns like “hers,” “its,” “theirs;” indefinite pronouns require one: e.g., one’s friend. 
    • In compounds, the ‘s is added to the word nearest the object of possession. 
    • Joint possession is shown by putting the apostrophe on the last word of a series, e.g., Abelard and Héloise’s child. 
    • The apostrophe follows the s of a word with two sibilant sounds; e.g., Kansas’ and Moses’. 
    • The apostrophe is not used in “Pikes Peak,” the mountain in Colorado. 

    Contractions: The apostrophe is used when leaving out a letter or number in a contraction. For example, “I can’t” (instead of “cannot”); “let’s dance” (instead of “let us”); “it’s a beautiful day in the neighborhood” (instead of “it is”). 


    • Plurals of letter abbreviations with periods and single letters use ‘s. For example: There are four s’s in . 
    • Plurals of letter combinations, numerals, and hyphenated nouns end in I with no apostrophe; for example: 1s and 0s. 
    • The apostrophe is not used in names of organizations unless actually part of the legal name. 

    Braces ({ }) are used to show the relationship of elements in a group. 

    Brackets ([ ]) are used to insert words in quoted matter, for explanatory, correctionary, or commentary reasons. 

    • Used to insert missing letters and to enclose insertions that take the place of or slightly alter the original text, e.g., [they] may replace a long list of names previously mentioned. Brackets are also used in unquoted matter for the same reasons. 
    • Used as parentheses within parentheses. 
    • Used in mathematical expressions (to show matter to be treated as a unit), chemical formulas, and for phonetic symbols. 

    Colon (:) 

    • Used to introduce explanatory information, lists; for salutations, as in “Dear so-and-so:” and in clock time “It was at 5:00 in the afternoon”; periodical reference (e.g., 4:3); and between book title and book subtitle (e.g., Dictionaries: The Art and Craft of Lexicography). 
    • Used before a final clause that explains, or amplifies something in that sentence, e.g., The dissertation needs work: it lacks flow. 
    • Introduces a series or summarizing statement (e.g., The following is on our list of places to go: grocery store, toy store, doughnut shop. /She had one great love: him.) 
    • Used in proportions, e.g., 2:1, and as a ratio sign, e.g., 1:2::3:6. 
    • May introduce a quotation, especially a long one. 
    • Used in dialogue text, e.g., Juliet: O Romeo, Romeo! Wherefore art thou Romeo? 
    • Used in correspondence for headings and introductory terms (To: From: Re:) and to separate writer/typist and carbon-copy abbreviation from the recipients. 

    Comma (,) is most commonly used to separate or set off items that might otherwise be misunderstood, such as: 

    • Members of a series used with “and,” “or,” or “nor.” 
    • Main clauses, or before the conjunction in a compound sentence. 
    • Two verb phrases in a sentence. 
    • Subordinate clauses/phrases within sentence. 
    • An apposite (noun referring to previous noun, e.g., my sister, Nancy) or contrasting words/phrases (e.g., I need you, not anyone else.) 
    • Introductory items, e.g., Sir, are you listening? 
    • Interrupting or parenthetic items. 
    • Before quotation following an introductory phrase, e.g.: She said quietly, “I love you.” 
    • Inside a closing quotation mark, e.g.: I said “wash,” not “drawer.” 
    • To show omission, e.g., The thing is, we need time. 
    • Between compound qualifiers, e.g., He has big, broad shoulders. 
    • Between name and title, title and organization, name and degree, surname and Junior/Jr./Senior/Sr. 
    • In an inverted name, e.g., Shakespeare, William; Kipfer, Barbara Ann. 
    • To separate thousands, millions, etc. in number of four or more digits, e.g., 2,000. 
    • To set off the day of the month, e.g., Their anniversary is June 1, 1991, when they met. 
    • To set off elements of an address, e.g., Write to him at The Language Centre, University of Exeter, Exeter, England EX4 4QH. 
    • After the salutation in informal correspondence, e.g., “Dear T.B.,” and after the complimentary close in all correspondence, e.g., “Respectfully,”.