Apostrophes Beyond the Basics: correct answers
Jump to answers ↓When you want to show that something belongs to someone, adding an apostrophe and an s is usually simple. However, the rules get more complex when two people own something together, when a noun is already plural, or when you are talking about time.
Joint vs. Separate Possession
When two or more people own something together (joint possession), you only add the apostrophe and s to the last name in the list. The single apostrophe shows that the ownership is shared.
However, if two people each own separate things (separate possession), you must add an apostrophe and s to every name to show that the items belong to them individually.
✅ Arthur and Merlin's shared apartment is on the third floor. (They share one apartment). ❌ Arthur's and Merlin's shared apartment is on the third floor.
✅ Mark's and Sarah's individual suitcases are by the door. (Mark has his suitcase, and Sarah has hers). ❌ Mark and Sarah's individual suitcases are by the door.
Irregular Plural Possessives
For regular plural nouns ending in s (like employees or babies), you simply add an apostrophe at the very end of the word to show possession: the employees' breakroom, the babies' toys.
But English has many irregular plural nouns that do not end in s—such as women, children, men, and mice. Because these words don't already end in an s, you must treat them like singular nouns and add 's.
✅ The children's educational toys are on the second floor. ❌ The childrens' educational toys are on the second floor.
✅ The mice's tiny footprints led straight to the cheddar vault. ❌ The mices' tiny footprints led straight to the cheddar vault.
Time Expressions and Compound Nouns
Apostrophes aren't just for people and animals; they are also used in time expressions to show duration or measurement. This acts as a replacement for the word "of" (e.g., a delay of three months becomes three months' delay). If the time period is singular, use 's. If the time period is plural, use s'.
✅ The astronaut reported a three months' delay. ❌ The astronaut reported a three month's delay. ✅ I will be ready in one hour's time.
For compound nouns (words made up of two or more words joined by hyphens), the rule is straightforward: always attach the 's to the very last word, regardless of which word is pluralized.
✅ The commander-in-chief's horse refused to move. ❌ The commander's-in-chief horse refused to move.
Common Mistakes: Whose vs. Who's and Nouns Ending in S
A frequent mistake is confusing the possessive pronoun whose with the contraction who's (which means who is or who has). Remember that possessive pronouns (yours, hers, ours, whose) never take apostrophes.
✅ I need to know whose half-eaten donut was left on the machine. ❌ I need to know who's half-eaten donut was left on the machine.
Finally, learners often freeze when a singular noun ends in s (like boss, princess, or bus). The most standard and widely accepted rule in modern English is to add 's, just as you would for any other singular noun. This matches how we pronounce the word, adding an extra "iz" sound at the end.
✅ The boss's new policy was highly unpopular. ❌ The bosses new policy was highly unpopular. ✅ The princess's missing tiara caused quite a scandal.
Correct answers
Question 1
Complete the detective's report about the great cheese heist.
The gang of rodents left a terrible mess. The ________ tiny footprints led straight to the cheddar vault.
The correct answer is mice's.
"Mice" is an irregular plural noun (it doesn't end in s). To make an irregular plural noun possessive, you treat it just like a singular noun: add an apostrophe followed by an s ('s).
Question 2
The correct answers are Mark and Sarah's shared apartment is on the third floor. and Mark's and Sarah's individual suitcases are by the door.
When two or more people own something together (joint possession), only the final name gets the apostrophe + s (Mark and Sarah's apartment).
When two or more people own separate things (separate possession), both names get an apostrophe + s (Mark's and Sarah's suitcases).
Question 3
whose half-eaten donut
Whose is the possessive form of who. Who's is a contraction for who is or who has, which doesn't make sense here ("who is half-eaten donut").
boss's new intern
Boss is a singular noun ending in s. To make it possessive, we add an apostrophe + s.
its pink frosting
Its (without an apostrophe) is a possessive pronoun showing ownership. It's (with an apostrophe) is always a contraction for it is or it has. Its' is never a real word!
Question 4
The correct answers are The Princess's missing tiara caused quite a scandal. and The commander-in-chief's horse refused to move.
Singular nouns ending in s (like Princess or Jones) usually take an apostrophe + s to show possession (Princess's, Mr. Jones's).
For compound nouns (like commander-in-chief or mother-in-law), the possessive apostrophe + s always goes at the very end of the phrase, not in the middle.
Question 5
Emma and Noah's shared locker
When two or more people share ownership of something (joint possession), only the final name gets the apostrophe + s.
men's breakroom
Men is already a plural noun, so we do not add an s before the apostrophe. To make an irregular plural noun possessive, we just add an apostrophe + s.
cafe's prized vintage espresso machine
The machine belongs to one single cafe, so we use the singular possessive form: apostrophe + s.
Question 6
Complete the real estate agent's property descriptions by choosing the correct possessive forms.
I just visited Lisa and Tom's new house, which they bought together last week. Unfortunately, Mark's and Sarah's separate cars were blocking the driveway, so I had to park on the street. The previous tenants had to give the landlord two weeks' notice before moving out.
I just visited Lisa and Tom's new house, which they bought together last week. Unfortunately, Mark's and Sarah's separate cars were blocking the driveway, so I had to park on the street. The previous tenants had to give the landlord two weeks' notice before moving out.
Lisa and Tom's: When two people own something together (joint possession), only the final name gets the apostrophe.
Mark's and Sarah's: When two people own separate things (individual possession, as indicated by "separate cars"), both names get an apostrophe.
two weeks': Time expressions can be possessive. Since "weeks" is a plural noun ending in "s", the apostrophe goes after the "s".
Question 7
Help the landlord address the correct tenants in his email by choosing the correct phrase.
The landlord finally agreed to fix the broken radiator in ________ shared apartment.
The correct answer is Arthur and Merlin's.
When two or more people own the same single item together (joint possession), we only add the apostrophe and "s" to the last name in the group. Because Arthur and Merlin share one apartment, it is "Arthur and Merlin's apartment."
If they each had their own separate apartment, you would use "Arthur's and Merlin's apartments."
Question 8
The correct answers are Women's Winter Coats and Babies' Accessories.
For irregular plural nouns that do not end in s (like women, men, children), you must add an apostrophe + s (Women's, Men's, Children's).
For regular plural nouns that already end in s (like babies), you only add an apostrophe at the end (Babies').
Question 9
Choose the correct phrase to complete the astronaut's space log.
After ________ delay, we are finally ready to launch this rocket to Mars!
The correct answer is three months'.
We use apostrophes in time expressions when the time period acts as a possessive adjective describing the noun (e.g., a delay of three months). Since "months" is a regular plural noun ending in s, we simply add an apostrophe to the end (months').
Question 10
Help the department store manager label the new floor plan correctly by dragging the right words into the blanks.
The new women's clothing section is located right next to the children's shoe department, just past the employees' break room.
The new women's clothing section is located right next to the children's shoe department, just past the employees' break room.
Because women and children are irregular plural nouns that do not end in "s", you must add an apostrophe followed by an "s" (women's, children's) to make them possessive.
Because employees is a regular plural noun that already ends in "s", you only add an apostrophe at the end (employees') to show possession.