Definition

1. Adjective:
   • Mortal, deadly: Describes something that is extremely hostile or incompatible to the point of being fatal or involving life and death. It conveys a sense of irreconcilable opposition or a feud that cannot coexist under the same sky.

Usage Examples

• Adjective:
  • Hai gia tộc đó có mối thù bất cộng đái thiên. (Those two clans have a mortal/deadly feud.)
  • Đó là một kẻ thù bất cộng đái thiên. (That is a mortal/deadly enemy.)

Advanced Usage

• This term is a classical, literary idiom derived from Chinese (不共戴天). It is used in formal, dramatic, or literary contexts to emphasize the utmost severity of a conflict or hatred. It is not used in casual, everyday conversation.
• The phrase literally means "not sharing the same sky to wear (as a hat)," poetically expressing that the enmity is so deep the parties cannot coexist in the same world.

Variants and Related Words

• Thù không đội trời chung: This is the more common Vietnamese vernacular phrase with the same meaning as "bất cộng đái thiên." It means "a feud of not sharing the same sky."
• Tử thù (n): Mortal enemy, deadly feud.
• Cực kỳ thù địch (adj): Extremely hostile.

Synonyms

• Không đội trời chung: Not sharing the same sky (the vernacular synonym).
• Sống mái: Life-and-death (often used for a decisive, final struggle).
• Tử thù: Mortal enmity.

Related Idioms

• Thù không đội trời chung: This is the primary related idiom and the standard way to express this concept in Vietnamese. It is used identically to "bất cộng đái thiên."
  • Hắn ta là kẻ thù không đội trời chung của tôi. (He is my mortal enemy, with whom I cannot share the same sky.)

1. Mortal, deadly