The soles are flatfishes of various families. Narrowly speaking, they are the members of the family Soleidae, but, outside Europe, the name 'sole' is also applied to various other similar flatfish, especially other members of the sole suborder Soleoidei as well as members of the flounder family.

In European cookery, there are several species which may be considered 'true' soles, but the common or Dover sole Solea solea, often simply called the 'sole', is the most esteemed and most widely available. (Davidson)

The name 'sole' comes from its resemblance to a sandal, Latin solea. In other languages, it is named for the tongue, e.g. German Zunge, Spanish lenguado.

The name 'sole' outside Europe presents a confusing picture. Davidson says:

In North America, the two names and flounder are applied in what seems like a haphazard manner across the whole range of flatfish.... So on seeing what we call a sole an American would be apt to describe it as a flounder. If served what we call a flounder he would probably wonder why it had been deprived of the more honorific title of sole. The situation is irremediable. (Davidson, 1972, p. 224)

Indeed, in North American restaurants, the name 'sole' is often used to name any small flatfish, especially when filleted.

Worldwide, members of several groups of flatfish are called 'soles'. A complete list can be found using Fishbase's search function. They include:

• In the sole suborder Soleoidei:
  • The true soles Soleidae, including the common or Dover sole Solea solea. These are the only fishes called 'soles' in Europe.
  • The American soles Achiridae, sometimes classified among the Soleidae.
  • The tongue soles or tonguesoles Cynoglossidae, whose common names usually include the word 'tongue'.
• Several species of righteye flounder in the family Pleuronectidae, including the lemon sole, the Pacific Dover sole, and the petrale sole.

Bibliography

• Alan Davidson, North Atlantic Seafood, 1979. ISBN 0670515248.
• Alan Davidson, Mediterranean Seafood, 1972. ISBN 1580084516.