The term “plantain” is loosely applied to any banana cultivar that is eaten when cooked. However, there is no formal botanical distinction between bananas and plantains. Cooking is also a matter of custom, rather than necessity. Ripe plantains can be eaten raw, since the starches are converted to sugars as they ripen. In some countries, there may be a clear distinction between plantains and bananas, but in other countries, where many more cultivars are consumed, the distinction is not made in the common names used. In more formal usage, the term “plantain” is used only for “true” plantains, while other starchy cultivars also used for cooking are called “cooking bananas”.
All modern plantain cultivars have three sets of chromosomes (i.e. they are triploid). Many are hybrids derived from the cross of two wild species, Musa acuminata and Musa balbisiana. The currently accepted scientific name for all such crosses is Musa × paradisiaca. Using Simmonds and Shepherds’ (1955) genome-based nomenclature system, cultivars which are cooked often belong to the AAB Group, although some (e.g. the East African Highland bananas) belong to the AAA Group, and others (e.g. Saba bananas) belong to the ABB Group.
Fe’i bananas (Musa × troglodytarum) from the Pacific Islands are often eaten roasted or boiled, and are thus informally referred to as “mountain plantains.” However, they do not belong to either of the two species that all modern cultivated banana cultivars descended from.