Default[f] gives the default value for arguments of the function f obtained with a _. pattern object. Default[f, i] gives the default value to use when _. appears as the ...

DefaultOptions is a style option that allows default options to be specified for particular formatting and related constructs.

DefaultButton[] represents an OK button that closes a dialog, and is the default when DynamicBox[ToBoxes[If[$OperatingSystem === "MacOSX", "Return", "Enter"], StandardForm], ...

DefaultElement is an option for Grid and related constructs which specifies what to insert when a new element is interactively created.

Sometimes you may want to set up functions where certain arguments, if omitted, are given "default values". The pattern x_:v stands for an object that can be omitted, and if ...

DefaultNewCellStyle is a notebook option which specifies the default style to use for new cells created in the notebook.

If you have installed Mathematica in a location where multiple users can run it (for example, on a file server or multi-user machine), then you can set up systemwide defaults ...

Default Kernel specifies the default kernel for all calculations.

Default View resets the view point for the selected (or clicked upon) 3D graphic to the default orientation.

Notebook's Default Context specifies the default context for the current notebook's kernel.