西格玛

六西格玛 (liù xīgémǎ, Six Sigma) is the most familiar context in Chinese business writing — the Motorola/GE quality-management methodology is a fixture in MBA curricula. Mathematical/statistical 西格玛 also appears in textbooks; in pop-culture business-speak, the English-loan slang 'sigma' (alpha-male meme) hasn't displaced it as a translation.

memory

西 (west) + 格 (frame/style) + 玛 (agate, used phonetically) — 'sig-ge-ma' approximates 'sigma'. The same 玛 closes 罗马 (Rome) and 巴拿马 (Panama).