<unk>  is a common non-scientific word which is most often applied to any gastropod mollusk whatsoever that has a very reduced shell, a small internal shell, or no shell at all. A<unk> -like body is an adaptation which has occurred many times in various groups of snails.
The common name "slug" is most often applied to land species, but the word has also been applied to many marine species. The largest group of marine shell-less gastropods or sea<unk> s are the nudibranchs, but there are in addition many other groups of sea<unk>  such as the heterobranch sea butterflies, sea angels, and sea hares, as well as the only very distantly related, pelagic, caenogastropod sea<unk> s, which are within the superfamily Carinarioidea.
Evolutionarily speaking, the loss or reduction of the shell in gastropods is a derived characteristic; the same basic body design has independently evolved several times, making<unk> s a strikingly polyphyletic group. In other words, the shell-less condition has arisen many times in the evolutionary past, and because of this, the various different taxonomic families of<unk> s are often not at all closely related to one another, despite a superficial similarity.
This article is primarily about pulmonate land<unk> s.
Slug
Spore
Stye
Flea
Floater
Boil
Wart
Wonder 