/ˈbɪɡəməs rɪˈleɪʃənʃɪp/ – Phrase
Definition: quan hệ song hôn.
A more throughout explanation: A bigamous relationship is a marital relationship in which one of the parties is already legally married to another person. This is considered illegal and void under the law.
Example: The individual was charged with bigamy after it was discovered that he had entered into a bigamous relationship by marrying another person while still legally married to his first spouse.