crystal grain; individual unit cell of a crystal
Technical term in materials science and crystallography. Refers to a single crystalline region within a polycrystalline material.
The strength of a metal is affected by the size of its crystal grains.
This alloy is hard because its crystal grains are fine.
Compound of 結晶 (crystal) + 粒 (grain). A straightforward technical term with no obscure historical derivation.