The orange and in particular the sweet orange is the fruit that derives from the citrus species Citrus X sinensis that belongs to the family of Rutaceae. The Citrus X sinensis can be divided into four subgroups, that each have their own characteristics: common oranges, navel oranges, blood/pigmented oranges and acid less oranges.
The orange is a hybrid and derives from pomelo (Citrus maxima) and mandarin (Citrus reticulata). Its genes can be traced to about 25% pomelo and some 75% mandarin. The hybrid however is not a basic backcrossed BC1 hybrid, but the orange is actually hybridized over multiple generations.
When it comes to the fruit of various kinds of oranges, the fruit of the Citrus X sinensis is regarded as a sweet orange, while the fruit of the Citrus X aurantium is recognized as a bitter orange.