yuanyang
A pair of mandarin ducks, one male and one female, as a symbol of faithful union.
countable, uncountable
The yuanyang are the male and female respectively of Anas galericulata, commonly called by Europeans "Mandarin duck." These beautiful water-fowl manifest when mated a singular degree of attachment for each other, and they have hence been elevated into the emblems of connubial affection and fidelity.
Where it comes from
Borrowed from Mandarin 鴛鴦 /鸳鸯 (yuānyāng, literally “male (鴛) and female (鴦) mandarin duck”).
Adapted from the Wiktionary entry yuanyang (CC BY-SA 4.0).