1For a currency, language, qualification, etc., to be in common, valid use and generally accepted; can also refer to a ticket or money actually being usable.
この地域では二つの言語が通用している。
Two languages are in common use in this region.
旧デザインの紙幣はもう通用しない。
Bills with the old design are no longer valid or in circulation.
この資格は海外でも通用しますか。
Is this qualification valid or recognized overseas as well?
回数券は来月末まで通用します。
This multi-ride ticket is valid until the end of next month.
2For a way of thinking, an excuse, or a method to be accepted and work in a given situation; commonly used as '~では通用しない' ("doesn't work/hold up in ~").
その言い訳は上司には通用しないだろう。
That excuse probably won't fly with your boss.
学生時代のやり方は社会人になっても通用するとは限らない。
The way you did things as a student doesn't necessarily work once you're a working adult.
彼の英語力は海外でも十分に通用する。
His English ability holds up perfectly well even abroad.
その理論は現代の経済にはもう通用しない。
That theory no longer applies to the modern economy.
3Refers to an entrance/exit of a building, as in 通用口 ('service entrance') - an entrance used routinely, e.g. by employees.
社員は正面玄関ではなく通用口を使う決まりだ。
Employees are required to use the service entrance instead of the main entrance.
配達業者は通用口から荷物を運び入れる。
Delivery workers bring packages in through the service entrance.