açaí (ä´säē´), tree, Euterpe oleracea, of the family Arecaceae (palm family) and its fruit, grown chiefly in Pará state in the Amazon region of Brazil. The trees can grow to 60 ft (18 m). the small, round, dark purple fruits are typically 1/2 in. (1.3 cm) in diameter. Initially collected from the wild, açaí is now cultivated on plantations; the tree and other trees in the genus Euterpe are also grown for hearts of palm. The pulp of the açaí fruit, botanically a drupe, or stone fruit, is often sweetened and frozen. An important part of the local diet for centuries, it has since 2000 enjoyed growing popularity as a dietary supplement. Although studies have shown that the fruit is a source of antioxidants, claims about specific health benefits are unproven.