A coffee bean (Arabic بُن bunn) is a seed of the coffee plant. It is the pit inside the red or purple fruit often referred to as a cherry. Even though they are seeds, they are incorrectly referred to as 'beans' because of their resemblance to true beans. The fruits - coffee cherries or coffee berries - most commonly contain two stones with their flat sides together. A small percentage of cherries contain a single seed, instead of the usual two. This is called a peaberry. Like Brazil nuts (a seed) and white rice, coffee seeds consist mostly of endosperm.[1] The two most economically important varieties of coffee plant are the Arabica and the Robusta; 75-80% of the coffee produced worldwide is Arabica and 20% is Robusta.[1] Arabica seeds consist of 0.8-1.4% caffeine and Robusta seeds consist of 1.7-4% caffeine.[2] As coffee is one of the world's most widely consumed beverages, coffee seeds are a major cash crop, and an important export product, counting for over 50% of some developing nations' foreign exchange earnings.[3] The United States imports more coffee than any other nation.[4] In 2009 the average person in the United States consumed 4.09 kg (9 lbs) of coffee.[5]