Either … or, Neither … nor
The word either may be used on its own as a determiner
(either door will lead out into the garden)
or as a pronoun
(either of the books is good reading).
when two alternatives are specified,
The word either is paired with the word or
to introduce the first and the second alternatives respectively.
“It is important that either and or are correctly placed
so that the structures following
each word balance and mirror each other”
“She either left the book in the hall or in the kitchen”,
which is not balanced –
the structure following the word either and
that following the word or are of different forms.
The corrected sentence would read:
“She left the book either in the hall or in the kitchen”, or
“She left the book in either the hall or the kitchen”.
Neither … nor:
When neither (the negative of either)
is used in a paired construction,
the other member of the pair is nor –
NOT or as is sometimes encountered
(neither he or she is going to the concert).
The same considerations for either … or
as noted above apply to neither … nor.