Font

A font is one specific version of a typeface: a particular weight, style and size. Helvetica is a typeface; Helvetica Bold at 12 points is a font.

The word comes from metal printing. Each size and style needed its own set of metal letters, and every single piece of type was called a sort.

Digital type removed that limit: one font file can be shown at any size. Designers still use "font" to mean a specific weight and style, such as Regular, Bold or Italic.