Null is the tag for the expression that represents nothing.
Although it seems useless, the Null expression is widely used, mainly while editing expressions
This expression must have no children.
While the visual representation of the Null expression must denote a senseless element, it must also have appreciable dimensions, in order to be distinguished as a sub-expression of a given expression.
There should not be editions to create a Null expression, given its senseless nature.
However, Null expressions are commonly created by other editions.
Since this expression is not expected to be reduced to a different one, no reducers are currently known.
Core Fōrmulæ library
The Null expression is the only expression that is implemented in the core Fōrmulæ library, instead of a package. So this implementation cannot be deleted or disabled.
There is one visualizalization for the Null expression.
This visualization shows a square. The dimensions of this square is 10 x 10 pixels, as shown: