The building blocks of English

Affixes

spher(o)-

Also sphaero‑.

A sphere; spherical.

Greek sphaira, ball.

A spherometer is an instrument for measuring the curvature of spheres and curved surfaces; something spheroid is a sphere-like but not perfectly spherical body; a spheroplast is a bacterium or plant cell bound by its plasma membrane. A related term is spherule, a small sphere (Latin sphaerula, a diminutive of Latin sphaera, sphere), from which comes spherulite, a small spheroidal mass of crystals, grouped radially around a point, found in obsidian and other glassy rocks. The spelling sphaero‑ is the older one, now almost entirely replaced by sphero‑.