1999NewA....4..489C

A "three-dimensional" classification for WN stars has been introduced by Smith, Shara, and Moffat (MNRAS 281, 163, 1996). In addition to the well known "one-dimensional" ionization subclasses (e.g., WN6, WN7, WN8, etc.) they have added subscripts of "h", "a", "b" and "o" to refer, respectively, to the connotation of hydrogen being present (from the Balmer/Pickering emission line decrement), the presence of absorption lines, the appearance of broad emission lines, or no evidence of hydrogen (in stars without a "b"). I will critically evaluate the appropriateness of the latter two subscripts, utilizing the observed distribution functions of line width and line strength for Galactic and LMC WN stars. A "two-dimensional" classification, providing information about the hydrogen in addition to the ionization is probably warranted.