Symbols are the basic named objects in Mathematica.
The name of a symbol must be a sequence of letters, letter-like forms and digits, not starting with a digit. Upper- and lower-case letters are always distinguished in Mathematica.
Conventions for symbol names.
Essentially all system-defined symbols have names that contain only ordinary English letters, together with numbers and $. The exceptions are , , , and .
System-defined symbols conventionally have names that consist of one or more complete English words. The first letter of each word is capitalized, and the words are run together.
Once created, an ordinary symbol in Mathematica continues to exist unless it is explicitly removed using Remove. However, symbols created automatically in scoping constructs such as Module carry the attribute Temporary which specifies that they should automatically be removed as soon as they no longer appear in any expression.
When a new symbol is to be created, Mathematica first applies any value that has been assigned to $NewSymbol to strings giving the name of the symbol, and the context in which the symbol would be created.
If the message General::newsym is switched on, then Mathematica reports new symbols that are created. This message is switched off by default. Symbols created automatically in scoping constructs are not reported.
If the message General::spell is switched on, then Mathematica prints a warning if the name of a new symbol is close to the names of one or more existing symbols.
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