Which is appropriate to use in which situation? I speak (and therefore write) “each other” all the time, but my copy editor often changes it to “one another.” I never remember to ask him why, and he’s not in today. (Plus, I don’t want to look too stupid.) Any rules here?
The sentence I’m editing that prompted this post:
According to the specs of my company, you’re right.
“Each other” is for two people
“One another” is for three or more people
Therefore it’s “The two women…trust each other’s taste” but “The men in the platoon had to learn to trust one another.”
I used to have a copy of Strunk and White in which I could look this up for you, but although my company frequently has some strange grammatical ideas, I think they’re right on this one.
Thanks, Palandine.
I think your usage is unimpeachable. Fowler’s Modern English Usage says of the distinction that Palandine mentions, “The differentiation is neither of present utility nor based on historical usage.”
Does Fowler’s also mention that the project manager will tear you a new one if you use “each other” for more than two or “one another” for less than three? 
There is one obvious example that goes contrary to the “rule” mentioned: “one another” is used in many traditional Christian wedding ceremonies.