first of the ten Heavenly Stems 十天干[shi2 tian1 gan1] / (used for an unspecified person or thing) / first (in a list, as a party to a contract etc) / letter "A" or roman "I" in list "A, B, C", or "I, II, III" etc / armor plating / shell or carapace / (of the fingers or toes) nail / bladed leather or metal armor (old) / ranking system used in the Imperial examinations (old) / civil administration unit in the baojia 保甲[bao3 jia3] system (old) / ancient Chinese compass point: 75°
to hit the target where it hurts (idiom) / fig. to hit home / to hit the nail on the head (in an argument)
切中要害
qiè zhòng yào hài
to hit the target and do real damage (idiom) / fig. to hit where it hurts / fig. to hit home / an argument that hits the nail on the head
秤砣虽小压千斤
chèng tuó suī xiǎo yā qiān jīn
although small, a steelyard weight may tip a hundred pounds (idiom) / apparently insignificant details can have a large impact / for want of a nail the battle was lost