In typography, the terms were set when all printing was done with metal type. Font or fount was all the letters or characters of a single size of a typeface. For example, all characters for 9-point Bulmer is a font, and the 10 point size would be another font.
With the increase in the use of personal computers, the definition of font has changed. The term font is now often used as another name for a typeface. The size of the characters has no effect on fonts when using this definition.