(2) is technically correct – “either” is singular – but the usage is changing. I am willing to bet that in another 100 years, no one will remember that “either” was once singular. It will be a vague their-linked thing. Of course the insistence on gender-neutral language, and the lack of a good gender-neutral pronoun set in English, drives this move to “their” as well.
FWIW, I wouldn’t say “suck their thumbs” but “suck their thumb” – using “their” as purely a gender-neutral replacement for his/her.
quote=“ironlady” is technically correct – “either” is singular – but the usage is changing. I am willing to bet that in another 100 years, no one will remember that “either” was once singular. It will be a vague their-linked thing. Of course the insistence on gender-neutral language, and the lack of a good gender-neutral pronoun set in English, drives this move to “their” as well.
FWIW, I wouldn’t say “suck their thumbs” but “suck their thumb” – using “their” as purely a gender-neutral replacement for his/her.[/quote]