Snail, a gastropod, especially one having an enclosing shell, into which it may retract completely for protection. A gastropod lacking a shell is commonly called a slug or sea slug.When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell (that they cannot retract into) are often called semi-slugs.
Snails have considerable human relevance, including as food items, as pests, and as vectors of disease, and their shells are used as decorative objects and are incorporated into jewelry.[1] The snail has also had some cultural significance, tending to be associated with lethargy. The snail has also been used as a metaphor: someone who is not moving fast enough is "slow as a snail." The snail is the same or similar shape as the Cochlea.Snails that respire using a lung belong to the group Pulmonata. As traditionally defined, the Pulmonata were found to be polyphyletic in a molecular study per Jörger et al., dating from 2010.[3] But snails with gills also form a polyphyletic group; in other words, snails with lungs and snails with gills form a number of taxonomic groups that are not necessarily more closely related to each other than they are related to some other groups.
