The orange (specifically, the sweet orange) is the fruit of the citrus species Citrus × sinensis in the family Rutaceae
The fruit of the Citrus × sinensis is considered a sweet orange, whereas the fruit of the Citrus × aurantium is considered a bitter orange. The sweet orange reproduces asexually (apomixis through nucellar embryony); varieties of sweet orange arise through mutations.
The tangerine (Citrus tangerina) is an orange-colored citrus fruit that is closely related to, or possibly a type of, mandarin orange (Citrus reticulata).
The name was first used for fruit coming from Tangier, Morocco, described as a mandarin variety. Under the Tanaka classification system, Citrus tangerina is considered a separate species.
A clementine (Citrus ×clementina) is a hybrid between a mandarin orange and a sweet orange, so named in 1902. The exterior is a deep orange colour with a smooth, glossy appearance. Clementines can be separated into 7 to 14 segments. Similarly to tangerines, they tend to be easy to peel.