Definition

1. Noun:
   • Water caltrop: The edible fruit of an aquatic plant (Trapa spp.), characterized by its hard, dark, horned shell and starchy white interior. It is a common floating plant in ponds and slow-moving rivers in Southeast Asia.
   • Water chestnut (in some contexts): While distinct from the Chinese water chestnut (Eleocharis dulcis), it is sometimes referred to by this name due to its similar aquatic habitat and starchy texture.

Usage Examples

• Noun:
  • Củ ấu thường được luộc chín để ăn. (Water caltrops are often boiled to eat.)
  • Trên mặt hồ phủ đầy lá và quả của cây củ ấu. (The lake's surface is covered with the leaves and fruits of the water caltrop plant.)
  • Củ ấu có vị bùi và béo. (Water caltrops have a nutty and rich flavor.)

Advanced Usage

• Botanical Context: The term specifically refers to the fruit of plants in the genus , notably (horned nut) or . It is not a true root vegetable but a drupe.

Variants and Related Words

• Cây củ ấu (n): The water caltrop plant itself.
  • Cây củ ấu sống ở ao hồ. (The water caltrop plant lives in ponds and lakes.)

Synonyms

• Water caltrop: The most precise English equivalent.
• Horn nut: Descriptive name referring to its shape.
• Bat nut: Another common name due to its resemblance to a bat's wings.
• Ling nut: Name used in some regions.

Related Cultural Context

• Street Food: In Vietnam, boiled or roasted water caltrops are a popular seasonal street snack, especially in autumn.
• Traditional Medicine: In some practices, it is believed to have cooling properties and is used in certain remedies.