diff --git a/src/arg_desc.jl b/src/arg_desc.jl
index 2aad42a5..51ae0d80 100644
--- a/src/arg_desc.jl
+++ b/src/arg_desc.jl
@@ -40,7 +40,7 @@ const _arg_desc = KW(
 :ribbon            	=> "Number or AbstractVector.  Creates a fillrange around the data points.",
 :quiver            	=> "AbstractVector or 2-Tuple of vectors.  The directional vectors U,V which specify velocity/gradient vectors for a quiver plot.",
 :arrow             	=> "nothing (no arrows), Bool (if true, default arrows), Arrow object, or arg(s) that could be style or head length/widths.  Defines arrowheads that should be displayed at the end of path line segments (just before a NaN and the last non-NaN point).  Used in quiverplot, streamplot, or similar.",
-:normalize         	=> "Bool or Symbol. Histogram normalization mode. Possible values are: false/:none (no normalization, default), true/:pdf (normalize to a PDF with integral of 1) and :density (only normalize in respect to bin sizes).",
+:normalize         	=> "Bool or Symbol. Histogram normalization mode. Possible values are: false/:none (no normalization, default), true/:pdf (normalize to a discrete Probability Density Function, where the total area of the bins is 1), :probability (bin heights sum to 1) and :density (the area of each bin, rather than the height, is equal to the counts - useful for uneven bin sizes).",
 :weights           	=> "AbstractVector. Used in histogram types for weighted counts.",
 :contours          	=> "Bool. Add contours to the side-grids of 3D plots?  Used in surface/wireframe.",
 :match_dimensions  	=> "Bool. For heatmap types... should the first dimension of a matrix (rows) correspond to the first dimension of the plot (x-axis)?  The default is false, which matches the behavior of Matplotlib, Plotly, and others.  Note: when passing a function for z, the function should still map `(x,y) -> z`.",