Every Zettelmarkup content consists of a sequence of Unicode code-points.
Unicode code-points are called in the following as **character**s.

Characters are encoded with UTF-8.
; Line
: A __line__ is a sequence of characters, except newline (U+000A) and carriage return (U+000D), followed by a line ending sequence or the end of content.
; Line ending
: A __line ending__ is either a newline not followed by a carriage return, a newline followed by a carriage return, or a carriage return.
Different line can be finalized by different line endings.
; Empty line
: An __empty line__ is an empty sequence of characters, followed by a line ending or the end of content.
; Space character
: The __space character__ is the Unicode code-point U+0020.