pi
n.
Greek letter, from Hebrew, literally "little mouth." As the name of the mathematical constant, from 1841 in English, used in Latin 1748 by Swiss mathematician Leonhart Euler (1707-1783), as an abbreviation of Greek periphereia "periphery." For the meaning "printer's term for mixed type," see pie(3).
词根：pi = holy
来自拉丁语的pi意为holy。同义词根有来自拉丁语的secr,sanct 和来自希腊语的hagi,hier。
同源词：
1. expiate（使变得非常神圣 ex(=out,intensive) + pi(=holy)）
vt. 赎罪；补偿过失
expiation n.赎罪;补偿
expiatory adj.赎罪的；补偿的
His guilt is so strong he feels he can never expiate his evil deeds.他犯下的罪行太重了，以至于他自己都觉得无法为自己的罪行赎罪。
2. pious
adj.虔诚的，笃信的；可嘉的
3. piety
n.（宗教上的）虔诚；（对国家、君主、父母等的）忠诚，孝顺
filial piety 孝心
4. impious
adj.不敬的；不虔诚的 *im<in(=not)
5. impiety
n.不虔诚；对神不敬（的言行） im<in(=not)