theorist

theory +‎ -ist

• (Received Pronunciation) IPA^(key): /ˈθɪəɹɪst/
• (General American) IPA^(key): /ˈθiːəɹəst/, /ˈθɪɹəst/
• (General Australian) IPA^(key): /ˈθɪəɹəst/, /ˈθiːəɹəst/

theorist (plural theorists)

1. Someone who constructs theories, especially in the arts or sciences.
   • 2012 January 1, Michael Riordan, “Tackling Infinity”, in American Scientist‎, volume 100, number 1, page 86:

     Some of the most beautiful and thus appealing physical theories, including quantum electrodynamics and quantum gravity, have been dogged for decades by infinities that erupt when theorists try to prod their calculations into new domains.

• theoretician (less common)
• theorizer / theoriser

• A-theorist, B-theorist

• Theriots, orthites, otterish, shortite, thorites