On the HSK 2 vocabulary list, at CEFR level A2.

tōng ㄊㄨㄥ

    • to go through
    • to know well
    • expert

      suffix

    • to connect
    • to communicate
    • open
    • to clear
    • classifier for letters, telegrams, phone calls etc

tòng ㄊㄨㄥˋ

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

Where 通 is used

Sources