BizWritingTip reader: “Can you explain the use of apostrophes with words ending in ‘s’? I often forget, e.g., Louis Braille’s system of writing or Louis’ system.”
BizWritingTip response: This is a grammar issue that has many writers baffled. But you are correct with your suggestions.
To make singular or plural nouns that do not already end in an “s” possessive, you add an apostrophe and an “s.” If the word is singular, the apostrophe goes inside the “s.” If the word is plural, then the apostrophe goes outside the “s.”
Manager’s meeting (one manager is hosting a meeting)
Managers’ meeting (more than one manager is hosting a meeting)
Louis Braille’s system of writing (the system of one Mr. Braille)
However, to form the possessive of a singular noun that ends in an “s” sound, you must listen to the pronunciation.
If you hear yourself adding a new syllable when you form the possessive, then add an apostrophe plus “s.”
But if the word is hard to pronounce when you add the extra syllable, then just add the apostrophe by itself.
Unfortunately, individual differences in pronunciation can cause confusion with this rule.
I generally find if the word is one syllable and ends in an “s” sound (e.g., boss, Chris, and Jones), then you add ‘s. If the word is composed of two syllables or more and ends in an “s” sound (e.g., Thomas or Louis), then add the apostrophe only.
And you thought knowing grammar rules would make things less confusing!