The orange (specifically, the sweet orange) is the fruit of the citrus species Citrus × sinensis in the familyRutaceae.^[2] The fruit of the Citrus sinensis is considered a sweet orange, whereas the fruit of the Citrus aurantium is considered a bitter orange. The orange is a hybrid, possibly between pomelo (Citrus maxima) and mandarin (Citrus reticulata), which has been cultivated since ancient times.^[3]

As of 1987, orange trees were found to be the most cultivated fruit tree in the world.^[4] Orange trees are widely grown in tropical and subtropical climates for their sweet fruit. The fruit of the orange tree can be eaten fresh, or processed for its juice or fragrant peel.^[5] As of 2012, sweet oranges accounted for approximately 70% of citrus production.^[6] In 2010, 68.3 million metric tons of oranges were grown worldwide, production being particularly prevalent in Brazil and the U.S. states of Florida^[7] and California.^[8]