TraceAbove is an option for Trace and related functions which specifies whether to include evaluation chains which contain the evaluation chain containing the pattern form ...
TraceOn
(Built-in Mathematica Symbol) TraceOn is an option for Trace and related functions which specifies when tracing should be switched on.
TracePrint[expr] prints all expressions used in the evaluation of expr. TracePrint[expr, form] includes only those expressions which match form. TracePrint[expr, s] includes ...
TrackedSymbols is an option to Refresh, Manipulate, and related functions that specifies which symbols should trigger updates when their values are changed.
TransformationFunctions is an option for Simplify and FullSimplify which gives the list of functions to apply to try to transform parts of an expression.
Update
(Built-in Mathematica Symbol) Update[symbol] tells Mathematica that hidden changes have been made which could affect values associated with a symbol. Update[] specifies that the value of any symbol could ...
$BaseDirectory gives the base directory in which systemwide files to be loaded by Mathematica are conventionally placed.
$ImportFormats gives a list of import formats currently supported in your Mathematica system.
$LibraryPath gives the default list of directories to search in attempting to find a library.
$MaxMachineNumber is the largest machine-precision number that can be used on a particular computer system.