[可以意会,不可言传 / 可以意會,不可言傳, kě yǐ yì huì, bù kě yán chuánㄎㄜˇ ㄧˇ ㄧˋ ㄏㄨㄟˋ, ㄅㄨˋ ㄎㄜˇ ㄧㄢˊ ㄔㄨㄢˊ] can be understood, but not described (成语 saw, from Zhuangzi 莊子|庄子); mysterious and subtle, See Also: 成语, 莊子, 庄子
[他山之石可以攻玉, tā shān zhī shí kě yǐ gōng yùㄊㄚ ㄕㄢ ㄓ ㄕˊ ㄎㄜˇ ㄧˇ ㄍㄨㄥ ㄩˋ] lit. the other mountain's stone can polish jade (成语 saw); to improve oneself by accepting criticism from outside; to borrow talent from abroad to develop the nation effectively
[星星之火,可以燎原, xīng xing zhī huǒ, kě yǐ liáo yuánㄒㄧㄥ ㄒㄧㄥ˙ ㄓ ㄏㄨㄛˇ, ㄎㄜˇ ㄧˇ ㄌㄧㄠˊ ㄩㄢˊ] a single spark can start a huge blaze (成语 saw); an insignificant cause can have a massive effect