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    The Apostrophe

    Elizabeth O'Brien

    Hello! I'm Elizabeth O'Brien, and my goal is to get you jazzed about grammar. 

    The Apostrophe

    The apostrophe has three purposes. Do you know them all? We'll go over all three, and I'll give you examples of each. Here we go!

    1. Forming Possessive Nouns

    2. Showing Omission of Letters or Numbers

    3. Forming Strange Plurals

     1. Forming Possessive Nouns

    Nouns name people, places, things, or ideas. When we want to show that a noun has possession of something, we use an apostrophe.

    Sometimes, we add ' + s to the word, and sometimes we just add an '. Here are the rules.

     Add ' + s if...

    • The noun you're making possessive does not end in -s.

    This is Mark's cat. (The cat belongs to Mark.)

    I can't find the children's toys. (The toys belong to the children.)

    I used my sister-in-law's recipe. (The recipe belongs to my sister-in-law.)

    • The noun you're making possessive is singular and ends in -s. (Singular means one.)

    Those are the bus's headlights. (The headlights belong to the bus.)

    I found my boss's glasses. (The glasses belong to my boss.)

    * Different style guides give different information for using apostrophes with nouns that end in s, so the best thing to do is consult a style guide and be consistent with its advice. 

    Add ' if...

    • The noun you're making possessive is plural and ends in -s. (Plural means more than one.)

    Don't go into the teachers' lounge. (The lounge is for the teachers.)

    I graded three students' papers. (The papers belong to the students.)

    Don't Add Anything

     Do not add apostrophes to pronouns that already show possession.

    Whose jacket is this?

    It might be his or hers.

     2. Showing Omission of Letters or Numbers

    To omit means to leave something out. Contractions are shortened forms of combined words. When we smoosh the words together, we leave out some of the original letters, and we use apostrophes to show where the letters are taken out. 

    don't  (don't = do not)

    shouldn't  (shouldn't = should not)

    Who's  (Who's = who is)

     could've  (could've = could have)

    o'clock (o'clock = of the clock)

    We also use them to show omitted numbers.

    My parents were born in '50. ('50 = 1950)

    Contractions & Sentence Diagramming

    Many contractions contain a helping verb plus the word not. When you diagram these contractions, you must split the words up so that the helping verb goes in the verb slot and the word not goes in an adverb slot. Not answers one of the adverb questions(To what extent?) You can write either n't or not.

    sentence diagram contraction
    sentence diagram

    He didn't write his name on his paper.

     3. Forming Strange Plurals

    We always use these to show plurals of lowercase letters.

    Dot your i's and cross your t's.

     Some style guides suggest them to form plurals in other strange situations.

    • Pluralizing certain words used as nouns (if's, yes's)
    • Pluralizing abbreviations that also use periods (M.D.'s, C.P.A.'s)
    • Pluralizing capital letters (C's, A's)

    It's Your Turn! 
    Apostrophe Exercise

    Directions: Find the words with errors and correct them. 

    1. Carls tent is the same as our's. 

    2. Sheilas' Scrabble game is missing six ts and four xs. 

    3. Without his glasses, David walked into the womens restroom. 

    4. The squirrels love to run through my father-in-laws yard.

    5. Enjoy the book. Its yours to keep!


    1. Carl's tent is the same as ours.

    2. Sheila's Scrabble game is missing six t's and four x's

    3. Without his glasses, David walked into the women's restroom. 

    4. The squirrels love to run through my father-in-law's yard.

    5. Enjoy the book. It's yours to keep!

    Psst! If you enjoy learning with video lessons, this is for you.

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    Other Helpful Resources

    Learn more about other punctuation rules here.