Apostrophe use can confuse even seasoned writers.
This post discusses the three primary functions of the apostrophe in English: the marking of the possessive case in nouns, the marking of the omission of one or more letters, and the marking of plurals of individual characters. (The obsolescence of apostrophes with abbreviations is also discussed.)
Apostrophes are employed in conjunction with the possessive s, as shown in the following examples:
Note, in the case of proper nouns ending in s, the distinction between the first example, which refers to a party hosted by the Thompson family, and the usage Thompson’s, which refers to something belonging to a particular Thompson.
Lack of attention to this distinction is the cause of frequent errors in signage, as when a sign referring to the inhabitants of a residence reads, “The Thompson’s.” This truncation of “the Thompson’s house” literally indicates that it is the house of the Thompson and therefore is incorrect; it should read, “The Thompsons’.”