lightness and darkness are vectors of 3 colours used in the *_mode_* themes for the for the text, axis.line (and axis.ticks), panel.grid, panel.background and plot.background etc.
linewidthness is a vector of 2 integers used in the *_mode_* themes for the linewidth of the axis.line (axis.ticks and legend.ticks) and panel.grid theme elements.
