Array Variable An array variable is a variable that groups multiple scalar variables together using a single name. Each of the individual scalar variables is accessed via an index.
Environment The environment is a set of variables that the shell passes to every program it starts.
Environment Variable An environment variable is a variable that is a member of the environment.
Exporting The process of placing a variable in the environment is called exporting.
Local Variable A local variable is a variable that is present within the current instance of the shell. It is not available to programs that are started by the shell.
Read-Only Variable A read-only variable is a variable whose value cannot be changed.
Scalar Variable A scalar variable can hold only one value at a time.
Shell Variable A shell variable is a variable that is set by the shell and is required by the shell to function correctly.
Unsetting Unsetting a variable removes it from the list of variables tracked by the shell.
Variable A variable is a word that holds a value. The value can be any text string.
Variable Substitution Variable substitution is the process by which the shell replaces the name of a variable with its value.