The apple is a tree and its pomaceous fruit, of the species Malus domestica in the rose family Rosaceae. It is one of the most widely cultivated tree fruits. It is a small deciduous tree reaching 5-12 m tall, with a broad, often densely twiggy crown. The leaves are alternately arranged, simple oval with an acute tip and serrated margin, slightly downy below, 5-12 cm long and 3-6 cm broad on a 2-5 cm petiole. The flowers are produced in spring with the leaves, white, usually tinged pink at first, 2.5-3.5 cm diameter, with five petals. The fruit matures in Autumn, and is typically 5-8 cm diameter (rarely up to 15 cm).

The word apple comes from the Old English word aeppel, which in turn has recognisable cognates in a number of the northern branches of the Indo-European language family. The prevailing theory is that "apple" may be one of the most ancient Indo-European words (*abl-) to come down to English in a recognisable form. The scientific name malus, on the other hand, comes from the Latin word for apple, and ultimately from the archaic Greek mālon (mēlon in later dialects). The legendary placename Avalon is thought to come from a Celtic evolution of the same root as the English "apple"; the name of the town of Avellino, near Naples in Italy is likewise thought to come from the same root via the Italic languages.