* 蛋黄酱 (dàn huáng jiàng) literally means "egg yolk sauce", and is the more common and direct translation.
* 美乃滋 (měi nǎi zī) is a transliteration of the French word "mayonnaise," and is less commonly used.
Therefore, if you're looking for mayo in a Chinese restaurant, it's best to ask for 蛋黄酱 (dàn huáng jiàng).