Keyword (key_word) 
Keyword (key_word). There is a difference between "normal" keywords (not_reserved_key_word) and reserved keywords (reserved_key_word).
Syntax
<key_word> ::= <not_reserved_key_word> | <reserved_key_word>
Explanation
Keywords can be entered in uppercase/lowercase characters. Generally speaking, key words should not be used to designate objects.
You can find a list of all “normal” key words (not_reserved_key_word) in the syntax list under not_reserved_key_word.
You can find
a list of all reserved key words (reserved_key_word) in the
syntax list under reserved_key_word.
You must not use reserved keywords as simple identifiers. However, you can use
reserved keywords as identifiers in the form of special
identifiers.
See also: