SubsuperscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for SubsuperscriptBox objects.
SuperscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for SuperscriptBox objects.
TraditionalFunctionNotation is an option for selections that specifies whether input of the form f(x) is interpreted by the kernel as a function or as a product.
UpperCaseQ[string] yields True if all the characters in the string are uppercase letters, and yields False otherwise.
$Aborted is a special symbol that is returned as the result from a calculation that has been aborted.
$Display gives a list of files and pipes to be used with the default $DisplayFunction.
$DynamicEvaluation is a symbol whose value is True if it is evaluated as part of the evaluation of a Dynamic.
$Failed
(Built-in Mathematica Symbol) $Failed is a special symbol returned by certain functions when they cannot do what they were asked to do.
$HomeDirectory gives your "home" directory.
$IgnoreEOF specifies whether Mathematica should terminate when it receives an end-of-file character as input.