Edit > Undo (Mathematica Menu Item)

Undo reverses the previous action, if possible.

Help > Why the Beep?... (Mathematica Menu Item)

Why the Beep? opens a dialog with an explanation of why the front end produced a beep.

First (Built-in Mathematica Symbol)

First[expr] gives the first element in expr.

ControlPlacement (Built-in Mathematica Symbol)

ControlPlacement is an option for Manipulate, TabView, and other control objects that specifies where controls should be placed.

PrintingPageRange (Built-in Mathematica Symbol)

PrintingPageRange is an option for notebooks that specifies the range of pages of a notebook to be printed.

LinearRegressionIndicator (Mathematica Indicator)

LinearRegressionIndicator

LinearRegressionSlope (Mathematica Indicator)

LinearRegressionSlope

RSquared (Mathematica Indicator)

RSquared

StandardError (Mathematica Indicator)

StandardError

AnimationDirection (Built-in Mathematica Symbol)

AnimationDirection is an option which specifies the direction to run an animation.