InsertResults is an option for NotebookEvaluate that determines whether to place the results of evaluation in the notebook being evaluated
IntervalIntersection[interval_1, interval_2, ...] gives the interval representing all points common to each of the interval_i.
ItemAspectRatio is an option for GraphicsGrid which specifies the ratio of height to width for the regions in which items are placed in the graphics grid.
JankoGroupJ3[] represents the sporadic simple Janko group J_3.
JankoGroupJ4[] represents the sporadic simple Janko group J_4.
Label
(Built-in Mathematica Symbol) Label[tag] represents a point in a compound expression to which control can be transferred using Goto.
Larger
(Built-in Mathematica Symbol) Larger is a style or option setting that specifies that objects should be larger.
LayerSizeFunction is an option for TreePlot that gives a function to specify the relative height to allow for each layer.
LeftArrow[x, y, ...] displays as x \[LeftArrow] y \[LeftArrow] ....
LeftRightArrow[x, y, ...] displays as x \[LeftRightArrow] y \[LeftRightArrow] ....