miscible

Miscible isn't simply a lesser-known synonym of mixable—it's also a cousin. It comes to us from the Medieval Latin adjective miscibilis, which has the same meaning as miscible and which derives, in turn, from Latin miscēre, meaning "to mix." Miscēre is also the ultimate source of our mix; its past participle mixtus (meaning "mixed") spawned mixte in Anglo-French and Middle English, and mix came about as a back-formation of mixte. The suffix -able gives us mixable, thereby completing its link to miscible. Miscible turns up most frequently in scientific discussions where it is used especially to describe fluids that don't separate when they are combined.