above by Top. In programming languages Most commonly used languages don't have a way to denote the bottom type. There are a few notable exceptions. In Haskell, The undefined constant or terms created with the error constructor may be assigned any type. Attempting to evaluate such an expression causes the code to abort unrecoverably. In Common Lisp the type NIL, contains no values and is a subtype of every type. The type named NIL is sometimes confused with the type named NULL, which has one value, namely the symbol NIL itself. In Scala, the bottom type is denoted as Nothing. Besides its use for functions that just throw exceptions or otherwise don't return normally, it's also used for covariant parameterized types. For example, Scala's List is a covariant type constructor, so List[Nothing] is a subtype of List[A] for all types A. So Scala's Nil, the object for marking the end of a list of any type, belongs to the type List[Nothing]. In Rust, the bottom type is called the never type and is denoted by !. It is present in the type signature of functions guaranteed to never return, for example by calling panic!() or looping forever. It is also the type of certain control-flow keywords, such as break and return, which do not produce a value but are nonetheless usable as expressions. In Ceylon, the bottom type is Nothing. It is comparable to Nothing in Scala and represents the intersection of all other types as well as an empty set. In Julia, the bottom type is Union{}. In TypeScript, the bottom type is never. In JavaScript with Closure Compiler annotations, the bottom type is !Null (literally, a non-null member of the Null unit type). In PHP, the bottom type is never. In Python, the bottom type is typing.NoReturn (typing.Never since version 3.11). In Kotlin, the bottom type is Nothing. In D, the bottom type is noreturn In Dart, since version 2.12 with the sound null safety update, the Never type was introduced as the bottom type. Before that, the bottom type used to be Null. See also Contradiction Fail-stop NaN Top type Unit type References Further reading Data types Type theory