References: https://www.grammarbook.com/punctuation/apostro.asp https://data.grammarbook.com/blog/apostrophes/apostrophes-with-words-ending-in-s/ Rule 1: Many common nouns end in the letter s (lens, cactus, bus, etc.). So do a lot of proper nouns (Mr. Jones, Texas, Christmas). There are conflicting policies and theories about how to show possession when writing such nouns. There is no right answer; the best advice is to choose a formula and stay consistent. Some writers and editors add ’s to every proper noun, be it Hastings’s or Jones’s. And there are a few who add only an apostrophe to all nouns ending in s—however, this method is relatively rare, and not recommended here. One method, common in newspapers and magazines, is to add an apostrophe plus s (’s) to common nouns ending in s, but only a stand-alone apostrophe to proper nouns ending in s. Examples: the class’s hours Mr. Jones’ golf clubs The canvas’s size Texas’ weather Another widely used technique, the one we favor, is to write the word as we would speak it. For example, since most people saying “Mr. Hastings’ pen” would not pronounce an added s, we would write Mr. Hastings’ pen with no added s. But most people would pronounce an added s in “Jones’s,” so we’d write it as we say it: Mr. Jones’s golf clubs. This method explains the punctuation of for goodness’ sake. Rule 2: To show plural possession of a word ending in an s or s sound, form the plural first; then immediately use the apostrophe. Examples: the classes’ hours the Joneses’ car guys’ night out two actresses’ roles