Mastering The Use Of S And S Clear Rules And Common Mistakes Explained

The apostrophe + s (’s) is one of the most frequently misused punctuation marks in written English. Whether indicating possession, forming contractions, or showing omission, the correct application of ’s affects clarity, professionalism, and readability. Despite its simplicity, confusion persists—especially between possessive forms and plural forms. This guide breaks down the essential rules, highlights frequent errors, and provides actionable strategies to help you use ’s accurately and confidently.

Understanding the Apostrophe + S: Core Functions

The combination of an apostrophe followed by the letter s serves three primary grammatical purposes:

1. Possession – Showing that something belongs to someone or something.
2. Contractions – Combining two words by omitting letters (e.g., “it’s” for “it is”).
3. Omission in time or measurement – As in “a day’s work” or “two weeks’ notice.”

Each function follows specific rules. Misapplying them leads to common errors such as writing “its” when you mean “it’s,” or adding an apostrophe to regular plurals.

Tip: If you're unsure whether to use an apostrophe, ask: Am I showing ownership or combining words? If not, no apostrophe is needed.

Rule 1: Forming Possessives with ’s

Possession indicates ownership. The basic rule is simple: add ’s to singular nouns and irregular plurals, and only an apostrophe to regular plural nouns ending in s.

Type	Example	Explanation
Singular Noun	the dog’s tail	Tail belongs to one dog → add ’s
Plural Noun (not ending in s)	the children’s toys	Toys belong to multiple children → add ’s
Plural Noun (ending in s)	the students’ books	Books belong to multiple students → add only apostrophe
Singular Name Ending in s	James’s car or James’ car	Both are acceptable; consistency matters more than preference

Note: For singular proper nouns ending in s, style guides differ. The Chicago Manual of Style recommends adding ’s (e.g., “Charles’s book”), while others allow just the apostrophe. Choose one approach and stick with it throughout your writing.

Rule 2: Contractions Using ’s

An apostrophe + s often replaces missing letters in contractions. The most commonly confused example is “it’s” vs. “its.”

• It’s = contraction of “it is” or “it has”
• Its = possessive form of “it”

This distinction trips up even experienced writers. Remember: if you can expand the word to “it is” or “it has,” use “it’s.” Otherwise, use “its.”

“It’s frustrating how often ‘its’ and ‘it’s’ are mixed up. But once you see ‘it’s’ as a shortcut, the rule becomes intuitive.” — Dr. Helen Reed, Linguistics Professor, University of Toronto

Other common contractions include:

• he’s = he is / he has
• she’s = she is / she has
• there’s = there is / there has
• who’s = who is / who has

A key insight: all these contractions involve third-person singular pronouns combined with “is” or “has.” Recognizing this pattern helps avoid misuse.

Common Mistakes and How to Avoid Them

Even native speakers make recurring errors with ’s. Here are the top three:

Mistake 1: Adding Apostrophes to Plurals

Incorrect: I bought three apple’s.
Correct: I bought three apples.

Apostrophes do not make words plural. This error, known as the “greengrocer’s apostrophe,” undermines credibility in professional writing.

Mistake 2: Confusing Possessive Pronouns

Incorrect: The dog wagged it’s tail.
Correct: The dog wagged its tail.

Pronouns like its, yours, hers, ours, theirs never take an apostrophe when possessive. Only their contracted forms (e.g., “it’s”) use one.

Mistake 3: Misplacing the Apostrophe in Joint vs. Separate Ownership

Joint ownership: Sarah and Tom’s project (one project they share)
Separate ownership: Sarah’s and Tom’s reports (two separate reports)

The position of the apostrophe clarifies whether ownership is shared or individual.

Tip: When in doubt, rephrase the sentence. “The project belongs to Sarah and Tom” suggests joint ownership → one ’s at the end.

Step-by-Step Guide to Correctly Using ’s

Follow this five-step process whenever you’re uncertain about using ’s:

1. Identify the word type – Is it a noun, pronoun, or contraction?
2. Determine purpose – Are you showing possession, forming a contraction, or indicating time/amount?
3. Check number – Is the noun singular or plural? Does the plural end in s?
4. Apply the rule – Use ’s for singulars and irregular plurals; use only apostrophe for regular plurals.
5. Test with expansion – For contractions, try expanding the word (e.g., “it’s” → “it is”). If it fits, the apostrophe is correct.

Real-World Example: A Business Email Gone Wrong

Consider this excerpt from a real client email:

“Thanks for attending yesterdays meeting. Its clear that everyones input was valuable, especially the marketing teams ideas.”

Three errors appear in just two sentences:

• “yesterdays” → should be “yesterday’s” (possessive: the meeting of yesterday)
• “Its clear” → should be “It’s clear” (contraction of “it is”)
• “everyones” → should be “everyone’s” (possessive: input belonging to everyone)
• “teams ideas” → should be “team’s ideas” (if one team) or “teams’ ideas” (if multiple teams)

Corrected version:

“Thanks for attending yesterday’s meeting. It’s clear that everyone’s input was valuable, especially the marketing team’s ideas.”

This small correction enhances professionalism and prevents misinterpretation.

Frequently Asked Questions

When do I use ’s for time expressions?

Use ’s to indicate a unit of time acting as a modifier. Examples: “a day’s notice,” “two weeks’ vacation,” “today’s news.” Note: For plural time units, the apostrophe comes after the s (e.g., “three years’ experience”).

What about names like “Jesus” or “Moses”?

For ancient or biblical names ending in s, many writers use just the apostrophe (e.g., “Jesus’ teachings”). However, adding ’s (“Jesus’s”) is also grammatically correct and increasingly accepted. Consistency within your document is key.

Can inanimate objects possess something?

Yes. Grammar allows inanimate nouns to show possession: “the car’s engine,” “the building’s entrance.” While some prefer rephrasing (“the engine of the car”), the possessive form is standard and concise.

Essential Checklist for Using ’s Correctly

Before finalizing any piece of writing, run through this checklist:

• ☐ No apostrophes used to form regular plurals (e.g., DVDs, not DVD’s)
• ☐ “It’s” only when meaning “it is” or “it has”
• ☐ “Its” used for possession (no apostrophe)
• ☐ Singular possessives use ’s (dog’s bowl)
• ☐ Regular plural possessives use only apostrophe (dogs’ bowls)
• ☐ Joint ownership uses one ’s; separate ownership uses two
• ☐ Time and measurement phrases follow possessive rules (a week’s pay)

Conclusion: Clarity Begins with Correct Punctuation

Mastering the use of ’s isn’t about memorizing obscure grammar rules—it’s about communicating clearly and professionally. Whether you’re drafting an email, writing a report, or posting on social media, accurate punctuation builds trust and credibility. The apostrophe + s may be small, but its impact is significant.

💬 Start today: Review your last written message and check every instance of ’s. How many were correct? Share your findings or questions in the comments—let’s build better writing habits together.