何

何时

hé shí

when

双曲几何

shuāng qū jǐ hé

hyperbolic geometry

黎曼几何

lí màn jǐ hé

(math.) Riemannian geometry

黎曼几何学

lí màn jǐ hé xué

Riemannian geometry

一部二十四史，不知从何说起

yī bù èr shí sì shǐ , bù zhī cóng hé shuō qǐ

It's a long and intricate story, I hardly know where to start.

不知何故

bù zhī hé gù

somehow

人生何处不相逢

rén shēng hé chù bù xiāng féng

it's a small world (idiom)

代数几何

dài shù jǐ hé

algebraic geometry

代数几何学

dài shù jǐ hé xué

algebraic geometry

任何

rèn hé

any; whatever; whichever

何不

hé bù

why not?

何不食肉糜

hé bù shí ròu mí

lit. "Why don't they eat meat?" (said by Emperor Hui of Jin 晉惠帝|晋惠帝[Jin4 Hui4 di4] when told that his people didn't have enough rice to eat)