Buoi is a Vietnamese term for grapefruit. In Vietnam, there are many tasty varieties of grapefruit. Ordinarily, the grapefruit is named for the locality where it is grown. For example , in the North, there is the Doan Hung grapefruit (Phu Tho Province), in the Central there is the Phuc Trach grapefruit (Ha Tinh Province), and in the South there is the Tan Trieu grapefruit (Bien Hoa Province). Each variety has a unique taste. The Phuc Trach grapefruit has the distinguishable sweet taste of the glucose that is dissolved in the fruit and a fresh taste that slightly permeates your body and makes your spirit light. There are many different scents and tastes of the Tan Trieu grapefruits. The thanh tra is mildly sweet and somewhat acidic. The buoi duong (grapefruit as sweet as sugar) is very sweet. The buoi xiem (Siamese grapefruit) has a rosy core and a light sweet taste.

In Dong Thap Province (Plain of Rushes), there is a variety of grapefruit that does not have any seeds, called nam roi. When it ripens, it bears a yellow colour and is as sweet as the buoi duong.