identifier Definition

A user-defined name in AHDL, Verilog HDL, or VHDL.

Type of Name	Legal Characters
Unquoted symbolic name (AHDL)	`a-z, A-Z, 0-9,` slash (`/`), and underscore (`_`). An unquoted symbolic name cannot consist entirely of digits and cannot be a reserved identifier or keyword.
Quoted symbolic name (AHDL)	`a-z, A-Z, 0-9`, slash (`/`), dash (`-`), and underscore (`_`). A quoted symbolic name cannot be a reserved identifier.
Identifier (VHDL)	`a-z, A-Z, 0-9`, and underscore (`_`). An identifier cannot begin with a digit or an underscore, cannot end with an underscore, and cannot have two underscores (`_ _`) in succession. It cannot be a keyword.
Identifier (Verilog HDL)	`a-z, A-Z, 0-9, $`, and underscore (`_`). An identifier cannot begin with a digit or `$`. Identifiers are case-sensitive. Verilog HDL keywords cannot be used.