Firstly it's helpful to understand what is meant by possessive. In grammatical terms, the possessive means "the case of nouns and pronouns expressing possession". And possession is defined as "owning something, controlling something, or having something". The thing that is owned doesn't have to be a physical item, it can be an emotion, an event, or some quality.
The rule to remember is that singular possession is shown by the use of "apostrophe s" — in other words, 's is added to the word. Here are some examples:
- Martha's new dress — the dress belongs to Martha
- George's party — the party was for George
- Mitten's trip to the vet — the trip "belongs" to Mittens
- The university's students — the students "belong" to the university
- My new car's tyres — the tyres belong on my car
- Coffee's aroma — the aroma is from or belongs to the coffee
- Jenny's happiness — the emotion is what Jenny has
- Max's evil plan — the plan belongs to Max, he thought it up all by himself (naughty boy!)
It can get a bit confusing when it comes to words that end in "s" too.
Strunk and White (in their classic The Elements of Style) state that you should follow the "apostrophe s" rule almost all the time:
- Charles's puppy
- Jess's knitting
The Australian Government's Style Guide for authors, editors, and printers (2002 edition) explains that there are various other rules floating around out there for singular words that end with "s". One states that you need to see how a possessive sounds before deciding whether to add an "apostrophe s" or just an apostrophe by itself. Another rule says that if the noun has only one syllable, it takes 's (eg Burns's) while if it has more than one syllable, just use the apostrophe by itself, after the final s (eg Dickens').
Burns's poems, or Burns' poems!? Dickens's novels or Dickens' novels!?
But in the end, the Style Manual also comes down in favour of simply adding "apostrophe s" regardless of the ending of a word. (So then Burns's and Dickens's are the correct usages.)
So if you're writing about a single thing, and what they have, use "apostrophe s". That's it! Easy!
Now you can go practise your possessives to get some practice in your newfound knowledge of possessives!
The Australian Oxford Dictionary (1999)
Strunk and White, The Elements of Style, Third Edition (1979)
Style Manual, Sixth Edition (2002)
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