Shell may refer to:

Architecture and design

Shell (structure) A shell is a three-dimensional solid structural element whose thickness is very small compared to its other dimensions. It is characterized in structural terms by mid-plane stress which is both coplanar and normal to the surface. A shell can be ...

, a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses

Science

Biology

Seashell A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. Most seashells are made by Mollusca, mollusks, such as snails, clams, and oysters ...

, a hard outer layer of a marine animal, found on beaches *

Eggshell An eggshell is the outer covering of a hard-shelled egg (biology), egg and of some forms of eggs with soft outer coats. Worm eggs Nematode eggs present a two layered structure: an external vitellin layer made of chitin that confers mechanical ...

* Nutshell *

Exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

, an external covering of some animals **

Mollusc shell The mollusc (or mollusk) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled ...

***

Bivalve shell A bivalve shell is the enveloping exoskeleton or mollusc shell, shell of a bivalve mollusc, composed of two hinged halves or ''valve (mollusc), valves''. The two half-shells, called the "right valve" and "left valve", are joined by a ligament and ...

***

Gastropod shell The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium ...

** Shell, of a

brachiopod Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear e ...

Turtle shell The turtle shell is a shield for the ventral and dorsal parts of turtles (the Order (biology), order Testudines), completely enclosing all the turtle's vital organs and in some cases even the head. It is constructed of modified bony elements such ...

Armadillo shell Armadillos () are New World placental mammals in the order Cingulata. They form part of the superorder Xenarthra, along with the anteaters and sloths. 21 extant species of armadillo have been described, some of which are distinguished by t ...

Physics and chemistry

Electron shell In chemistry and atomic physics, an electron shell may be thought of as an orbit that electrons follow around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (o ...

or a principal energy level of electrons outside an atom's nucleus *

Nuclear shell model In nuclear physics, atomic physics, and nuclear chemistry, the nuclear shell model utilizes the Pauli exclusion principle to model the structure of atomic nuclei in terms of energy levels. The first shell model was proposed by Dmitri Ivanenk ...

, a principal energy level of nucleons within an atom's nucleus *

On shell and off shell In physics, particularly in quantum field theory, configurations of a physical system that satisfy classical equations of motion are called on the mass shell (on shell); while those that do not are called off the mass shell (off shell). In quantu ...

, quantum field theory concepts depending on whether classical equations of motion are obeyed

Mathematics

Spherical shell In geometry, a spherical shell (a ball shell) is a generalization of an annulus to three dimensions. It is the region of a ball between two concentric spheres of differing radii. Volume The volume of a spherical shell is the difference between ...

Organisations

Shell plc Shell plc is a British Multinational corporation, multinational petroleum, oil and natural gas, gas company, headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and second ...

formerly Royal Dutch Shell plc, a British multinational oil and gas company ** Shell Oil Company or Shell USA ** Shell Australia ** Shell Canada ** Shell Nigeria *

Shell corporation A shell corporation is a company or corporation with no significant assets or operations often formed to obtain financing before beginning business. Shell companies were primarily vehicles for lawfully hiding the identity of their beneficial ...

, a type of company that serves as a vehicle for business transactions

Computing

Shell (computing) An operating system shell is a computer program that provides relatively broad and direct access to the system on which it runs. The term ''shell'' refers to how it is a relatively thin Abstraction layer, layer around an operating system. A sh ...

, a type of user interface **

Command-line interface A command-line interface (CLI) is a means of interacting with software via command (computing), commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user ...

, sometimes referred to as command shell **

List of command-line interpreters This list includes notable command-line interpreters programs that interactively interpret commands entered by the user at the command-line. Operating system shells Most operating systems are accessible via a shell a command line interp ...

, programs occasionally referred to as shells **

Web shell A web shell is a Shell (computing), shell-like interface that enables a web server to be remotely accessed, often for the purposes of cyberattacks. A web shell is unique in that a web browser is used to interact with it. A web shell could be pro ...

, interface that enables a web server to be remotely accessed *

Read–eval–print loop A read–eval–print loop (REPL), also termed an interactive toplevel or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user; a program written ...

, also known as a language shell *

Shell account A shell account is a user account on a remote server, typically running under Unix or Linux operating systems. The account gives access to a text-based command-line interface in a shell, via a terminal emulator. The user typically communicates w ...

, a user account on a remote server *

Secure Shell The Secure Shell Protocol (SSH Protocol) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution. SSH was designed for ...

, cryptographic network protocol *

Shellsort Shellsort, also known as Shell sort or Shell's method, is an in-place algorithm, in-place comparison sort. It can be understood as either a generalization of sorting by exchange (bubble sort) or sorting by insertion (insertion sort). The method s ...

or Shell sort, a sorting algorithm by Donald Shell * Shell, an empty

expert system In artificial intelligence (AI), an expert system is a computer system emulating the decision-making ability of a human expert. Expert systems are designed to solve complex problems by reasoning through bodies of knowledge, represented mainly as ...

Entertainment

* ''Shell'' (2012 film), an independent drama film * ''Shell'' (2024 film), an American thriller film * Shell (theater), a curved surface for reflecting sound * The Shells, a musical group * "Shell (Of a Man)", a song by Saya Gray from ''SAYA'', 2025 * "Shells" (''Angel''), a TV episode * "The Shell" (''The Amazing World of Gumball''), a TV episode * Shell, a receptacle used in the Shell game * "Shell", a song by Arrested Development from '' Zingalamaduni''

Places

* Shell, Ecuador *

Shell, Worcestershire Shell is a hamlet in the civil parish of Himbleton, in the Wychavon district, in the county of Worcestershire, England. It is 7 miles from Worcester, England, Worcester. In 1881 the parish had a population of 38. History The name "Shell" mean ...

, England * Shell, Wyoming, United States * Shell Lake (disambiguation), several places

Weaponry

Shell (projectile) A shell, in a modern military context, is a projectile whose payload contains an explosive, incendiary device, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military ...

, an explosive device fired from artillery * Shotgun shell, a type of shotgun ammunition

Persons with the surname Shell

* Art Shell (born 1946), American football player and coach * Brandon Shell (born 1992), American football player * Donald Shell (1924–2015), American computer scientist * Donnie Shell (born 1952), American football player * George Shell (disambiguation) * Karl Shell (born 1938), American economist *

Rita Shell Rita Shell (, Henrietta Shell; in private life, Mrs. John Stewart; nickname A nickname, in some circumstances also known as a sobriquet, or informally a "moniker", is an informal substitute for the proper name of a person, place, or thing, used ...

(1863–1950), British magazine editor

Other uses

Racing shell In watercraft, a racing shell (also referred to as a ''fine boat'' (UK) or simply a ''shell'') is an extremely narrow, and often comparatively long, rowing boat specifically designed for Rowing (sport), racing or exercise. It is equipped with lon ...

, a watercraft * Shell (machinery), each half of a two-piece plain bearing * Coverage shell, the number of defenders guarding the deep portion of the field in American football * Conchiglie, a type of pasta