大行其道

rampant / very popular

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

row / line / commercial firm / line of business / profession / to rank (first, second etc) among one's siblings (by age) / (in data tables) row / (Tw) column

to walk / to go / to travel / a visit / temporary / makeshift / current / in circulation / to do / to perform / capable / competent / effective / all right / OK! / will do / behavior / conduct / Taiwan pr. [xing4] for the behavior-conduct sense

road / path / CL:條|条[tiao2],股[gu3] / principle / truth / morality / reason / skill / method / Dao (of Daoism) / to say / to speak / to talk / classifier for long thin things (rivers, cracks etc), barriers (walls, doors etc), questions (in an exam etc), commands, courses in a meal, steps in a process / (old) circuit (administrative division)

his / her / its / their / that / such / it (refers to sth preceding it)