Final answer:
Superscript is not a font style; it is a typographic term for characters set above the normal line of type, unlike Bold, Regular, or Italic which are actual font styles.
Step-by-step explanation:
The option that is not a font style among Bold, Regular, Superscript, or Italic is Superscript. While Bold, Regular, and Italic are styles used to change the appearance of text to convey a certain tone or emphasize certain content, Superscript is actually a typographic term that refers to characters set slightly above the regular typing line. It is used for footnotes, endnotes, and mathematical or scientific notations, such as exponents. It does not change the thickness or slant of the text's characters like the other font styles do.
Typography is an essential aspect of design, and includes the choice of typefaces and consideration of their structural features, such as serifs and letterform thickness. The design of typefaces has evolved significantly from the days of physical typesetting to the modern digital era. Fonts like Helvetica represent sans-serif typefaces which are perceived as more modern, while serif fonts are seen as more classical.