2.3 Identifiers
Syntax
identifier_start ::= 
     letter_uppercase
   | 
letter_lowercase
   | 
letter_titlecase
   | 
letter_modifier
   | 
letter_other
   | 
number_letter 
identifier_extend ::= 
     mark_non_spacing
   | 
mark_spacing_combining
   | 
number_decimal
   | 
punctuation_connector 
An 
identifier 
shall not contain two consecutive characters in category 
punctuation_connector, 
or end with a character in that category. 
 
Static Semantics
Two 
identifiers 
are considered the same if they consist of the same sequence of characters 
after applying locale-independent simple case folding, as defined by 
documents referenced in the note in Clause 1 of ISO/IEC 10646:2011.
 
 
  After applying simple case folding, an 
identifier 
shall not be identical to a reserved word. 
 
Implementation Permissions
In a nonstandard mode, an implementation may support 
other upper/lower case equivalence rules for 
identifiers, 
to accommodate local conventions. 
 
2  
Identifiers 
differing only in the use of corresponding upper and lower case letters 
are considered the same. 
 
Examples
Examples of identifiers: 
Count      X    Get_Symbol   Ethelyn   Marion
Snobol_4   X1   Page_Count   Store_Next_Item
Πλάτων      -- Plato
Чайковский  -- Tchaikovsky
θ  φ        -- Angles
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