1. The ubiquitous use of “they” or “their” referring to a singular antecedent*. This has become the standard way to avoid the formerly ubiquitous (and clumsy) use of “he or she” and “his or her”, in order to be politically correct. For centuries before Women’s Liberation it was considered correct to let the male pronoun represent a member of a group of mixed or unspecified gender, or a single person of unspecified gender.
*Singular antecendents: each (person), everyone, anyone, one, no one, someone, and strangely enough, “each and every (person).”
Incorrect: “Everyone should bring their own lunch.”
Acceptable: “Everyone should bring his or her own lunch.”
Correct: “Everyone should bring his own lunch.”
All of these now sound awkward. There are, of course, work-arounds.
“Bring your own lunch.”
“Everyone should bring a lunch.”
“Those attending should bring their own lunches.”
“Lunch will not be provided.”
Personally, I prefer using a gender-neutral pronoun, such as “e” and “ez.”
“E should bring ez own lunch.”
I really don’t think this will catch on, however.
2. The use of the apostrophe before the terminal S in plurals.
“Car’s”, “piano’s”, or even “toe’s” (These are incorrect, even if meant as the possessive form, such as “the car’s windshield” or “the piano’s keys.” An object cannot be said to possess anything.)
“Dog’s” (This is correct only in the possessive form, such as “the dog’s ear.”)
“It’s” (This is the worst and most prevalent misuse of the apostrophe. It is only correct when used as a contraction for “it is.” Unlike other possessives, this gender-neutral pronoun forms a possessive only when no apostrophe is used, probably to distinguish it from the contraction.)
Now, I’ll bet that anyone who reads this will begin to notice how many apostrophes are applied incorrectly, even in professionally painted signs, and will try to correct ez own errors.