通商

having trading relations (of nations or regions)

to go through / to know well / (suffix) expert / to connect / to communicate / open / to clear / classifier for letters, telegrams, phone calls etc

classifier for an activity, taken in its entirety (tirade of abuse, stint of music playing, bout of drinking etc)

Shang Dynasty (c. 1600-1046 BC) / surname Shang

commerce / merchant / dealer / to consult / 2nd note in pentatonic scale / quotient (as in 智商[zhi4 shang1], intelligence quotient)

the five treaty ports forced on Qing China by the 1842 treaty of Nanjing 南京條約|南京条约 that concluded the First Opium War, namely: Guangzhou 廣州|广州, Fuzhou 福州, Ningbo 寧波|宁波, Xiamen or Amoy 廈門|厦门 and Shanghai 上海

treaty port, forced on Qing China by the 19th century Great Powers