Which form is correct in the following sentence?
Greek sigmas have a different form at the end of words?
Greek sigmas have a different form at the ends of words?
Which form is correct in the following sentence?
Greek sigmas have a different form at the end of words?
Greek sigmas have a different form at the ends of words?
Incrementally simplify your sentence to figure it out:
Greek sigmas have a different form at the ___ of words.
Sigmas have a form at the ___ of words.
So now you have:
[plural noun] have a [singular noun] at the ___ of [plural noun].
If all of the words share a single end, then the correct phrase is:
...at the end of words.
But if each word has its own end, then the correct phrase is:
...at the ends of words.
Since each word does have its own end, the second form is correct, and your sentence should read:
Greek sigmas have a different form at the ends of words.
However, I would personally suggest rewording for clarity:
Greek sigmas have a different form at the end of a word.
...which removes the ambiguous issue altogether. :-)