Time, Distance, and Value Expressions — English Grammar Exercises
boss's or bosses'? Tom and Sarah's or Tom's and Sarah's? — own it
Possessive Time, Distance, and Value Expressions
English uses the possessive structure to express the relationship between a quantity of time, distance, or money and what it produces, costs, or measures. Phrases like a week's holiday, six months' salary, and ten minutes' walk appear in formal and informal English alike. Analysis of the British National Corpus finds that time possessives are among the twenty most frequent possessive patterns in everyday written English, yet many learners omit the apostrophe entirely in these expressions, treating them as compound nouns.
Singular Time Expressions → 's
Singular time nouns and specific time adverbs take standard possessive 's:
a week's holiday | a day's work | a good night's sleep | one hour's sleep
Plural Time Expressions → s'
When the time noun is already plural, add only an apostrophe after the -s, exactly as with plural possessive nouns:
six months' salary | five years' experience
Value and Salary Expressions
The same pattern extends to monetary and quantity values: a pound's worth of sweets, a million dollars' worth of property. The possessive signals the relationship between the quantity and what it measures.
Common Mistakes
✗ We're going on three weeks holiday. → ✓ We're going on three weeks' holiday. (plural — apostrophe after s)
✗ She got a weeks holiday for Christmas. → ✓ She got a week's holiday. (singular — 's required)
Frequently Asked Questions
When do you add 's and when do you add just an apostrophe (s')?
The rule depends on whether the noun is singular or plural and how the plural is formed. Singular nouns — including those ending in -s — add 's: the boss's office, James's car. Regular plural nouns already ending in -s add only an apostrophe after the -s: the students' essays, my parents' house. Irregular plural nouns that do not end in -s add 's: children's playground, women's changing room, people's opinions. The key question is: what is the base plural form? If it ends in -s, add only an apostrophe. If it doesn't, add 's.
When do you use 's and when do you use an of-phrase?
's is the natural choice for people, animals, organisations, institutions, and time/distance/value expressions: the director's office, the government's decision, a week's holiday. The of-phrase is more natural with inanimate objects and physical parts of things: the roof of the house, the beginning of the film, the colour of the sky. For parts of objects, English also frequently uses compound nouns with no apostrophe: table leg (not table's leg), car door handle (not car's door handle). The rule of thumb: if you can replace it with a person's name, use 's. If the owner is an inanimate object, prefer of or a compound noun.
What is joint possession and how do you show it with apostrophes?
Joint possession means two or more people share a single item. In that case, only the last name takes 's: Tom and Sarah's wedding (one shared wedding). Separate possession means each person has their own. In that case, every name takes 's: Mark's and Lisa's offices (different offices). The grammar follows the logic: if one apostrophe covers both people, it must go on the final name in the pair. If each person owns their own item independently, each name needs its own possessive marker.
What is the double genitive and why is 'a friend of Sarah's' correct?
The double genitive (also called the 'of-possessive') is the construction: a/an + noun + of + possessive. 'A friend of Sarah's' means one of Sarah's friends — the possessive 's is required because the sentence implies Sarah has multiple friends and you are referring to one of them. Without the 's, the meaning changes: 'a friend of Sarah' would suggest the friend is somehow about Sarah or depicts her. The pattern extends to pronouns (a friend of mine, a colleague of yours) and to plural names (a neighbour of the Smiths'). The double genitive is obligatory when the indefinite article a/an precedes the noun.