#syzygy

Syzygy is a funky looking word for sure, but I quite like it. There are a lot of definitions for it depending on what sort of academic interests you have, ranging from mathematics and science to philosophy and psychology, but the thing they typically have in common is a pairing of opposites of some kind. The traditional definition comes from astronomy, where it refers to three celestial bodies aligning into a straight line. In our solar system, we might observe this during either a solar or lunar eclipse, where the three bodies in question are the earth, sun and moon. 

The word is likely an English adoption from about 1847, coming through Latin from the Greek term συζυγία suzugia, or “paired, yoked together, union.” This is a form of the noun σύζυγος suzugos which is defined with “yokefellow” (an interesting word by itself) and “spouse, couple (as in married pair as a couple)." 

The credited Proto-Indo-European root is yewgori̯eu alternately, both meaning "to tie together or yoke." One source I looked at remarked upon this being similar to a few other roots including "to keep separate” and “right or justice,” both of which are interesting to think about.