Helvetica is not the "font," but the "face."

I know what you mean... but in the case of Helvetica, it's actually both a face and a font name, because the "regular" version is simply named Helvetica, not Helvetica-Regular (as is the naming convention with some other faces). More precisely, the four Helvetica variants included in the "Base 14" font set (defined by Adobe) are named:

Helvetica
Helvetica-Bold
Helvetica-BoldOblique
Helvetica-Oblique

Anyhow, all I wanted to point out is that the term "sans serif" merely refers to the family of typefaces having "no serifs"...