TotalWidth is an option which can be set for output streams to specify the maximum total number of characters of text that should be printed for each output expression. Short ...
Unevaluated[expr] represents the unevaluated form of expr when it appears as the argument to a function.
WindowFrame is a notebook option that specifies the type of frame to draw around the window in which the notebook is displayed on the screen.
ZeroTest is an option to various linear algebra functions that gives a function to use in testing whether symbolic expressions should be treated as zero.
$FrontEndSession is a global symbol that represents the current session of the front end from which the kernel is being run.
$NewSymbol is a global variable which, if set, is applied to the name and context of each new symbol that Mathematica creates.
$NumberMarks gives the default value for the option NumberMarks, which specifies whether ` marks should be included in the input form representations of approximate numbers.
$Post
(Built-in Mathematica Symbol) $Post is a global variable whose value, if set, is applied to every output expression.
$TemporaryDirectory gives the main system directory for temporary files on your computer system.
$TimeZone gives the current time zone to assume for dates and times.