通信

to correspond (by letter etc) / to communicate / communication

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)

letter / mail / CL:封[feng1] / to trust / to believe / to profess faith in / truthful / confidence / trust / at will / at random