# Using plural for two individual objects of the same kind

Assume Einstein conjectured something (in Mathematics) and Zweistein conjectured something slightly stronger (implies Einstein's conjecture).

Which one of the following is correct?:

``````(a) Every X satisfies Zweistein's and thus Einstein's conjecture.
(b) Every X satisfies Zweistein's and thus Einstein's conjectures.
``````

``````(a) Every X satisfies Zweistein's and Einstein's conjecture.
(b) Every X satisfies Zweistein's and Einstein's conjectures.
``````

I went with (a), but was corrected by a native speaker. My feeling was that there are two separate identities and that "Zweistein's and Einstein's conjecture" is short for "Zweistein's conjecture and Einstein's conjecture".

• Suppose we rewrite as "Every X satisfies the conjecture of Einstein and the conjecture of Zweistein". That is unambiguous. However as soon as you try to combine the two as "the conjectures of Einstein and Zweistein" it's impossible to recover the original info that it was one each. So my conclusion is that you should write it out in full, repeating conjecture. – user24964 Nov 15 '13 at 15:46
• I would also use therefore instead of thus here. The two words are actually different and thus is really over used in scientific writing. Many people think it just sounds more official but it actually means in this manner rather than for this reason. – terdon Nov 15 '13 at 15:55
• @terdon I disagree, therefore is used everywhere in math and science. Much more often than I see thus anyway – Cruncher Nov 15 '13 at 19:32