Streams[] gives a list of all streams that are currently open. Streams["name"] lists only streams with the specified name.

Temporary is an attribute assigned to symbols which are created as local variables by Module.

Top is a symbol that represents the top for purposes of alignment and positioning.

TransferFunctionZeros[tf] gives a matrix of roots of the numerators in the TransferFunctionModel object tf.

TrueQ[expr] yields True if expr is True, and yields False otherwise.

UnderscriptBoxOptions -> {opt_1 -> val_1, opt_2 -> val_2, ...} is an option for selections that specifies settings for UnderscriptBox objects.

Visible is a notebook option which specifies whether the notebook should be explicitly displayed on the screen.

WindowClickSelect is a notebook option that specifies whether the window for the notebook should become selected if you click it.

WindowFloating is a notebook option that specifies whether the window for the notebook should float on top of other windows when it is displayed on the screen.

WindowToolbars is a notebook option that specifies the toolbars to include at the top of the window used to display the notebook on the screen.