From Latin bi- 'two' + laterālis 'of the side,' first anatomical, then diplomatic.
Having or relating to two sides; affecting or involving two parties, especially in agreements between nations.
From Latin bi- 'two' + laterālis 'of or belonging to the side,' from latus 'side.' First used in anatomy to describe symmetry, then adopted into diplomacy and law by the early 19th century. Key roots: *dwi- (Proto-Indo-European: "two"), *latus (Latin: "side, flank").