type theory - When does a font become a font?

As an offshoot of this interesting question, "Wire" (one dimensional) font, I'd like to ask, when does a Font become a Font?

What are the minimum requirements to call something a font? Can it exist without thickness? What about depth?

In Illustrator if I type the letter "A" it is certainly a font.

• Is it still a font if I expand it to be a path?


• Is it still a font if I expand it to be a path with no stroke or fill?


• If I draw a shape that resembles the letter "A" only using the pen tool (no type tool) then is that A a font?

Answer

Out of curiosity, I looked up what Wikipedia has to say about fonts:

In metal typesetting, a font is a particular size, weight and style of a typeface. Each font was a matched set of type, one piece (called a "sort") for each glyph, and a typeface comprised a range of fonts that shared an overall design.

In modern usage, with the advent of digital typography, "font" is frequently synonymous with "typeface", although the two terms do not necessarily mean the same thing. In particular, the use of "vector" or "outline" fonts means that different sizes of a typeface can be dynamically generated from one design. Each style may still be in a separate "font file"—for instance, the typeface "Bulmer" may include the fonts "Bulmer roman", "Bulmer italic", "Bulmer bold" and "Bulmer extended"—but the term "font" might be applied either to one of these alone or to the whole typeface.

https://en.wikipedia.org/wiki/Font

Now if we were talking about physical fonts from metal typesetting, obviously if the weight was so thin as to be non existent, then you just have a flat metal block and nothing would get printed. So kind of pointless. In this case, no thickness, no font.

The question of zero weight font only makes any sense in the digital realm. Then it would be effectively a vector path with no pixel width. I guess you could argue that it's a font if the vector path describes a family of glyphs, but it's still kinda pointless, because you still can't render it because there are zero pixels.

If you increase the weight (or pixel count, or whatever we are calling it) until the glyph becomes visible (min 1 pixel, I guess), then we are talking fonts.

But font's aren't just vector graphics, and you can't just scale them up and down as you like. Some web browsers will render an italic font simply by applying a skew effect to the base font. But that's not necessarily the same as the actual italic version of that font which a designer may have specifically developed. It's the same with font width. You can't just scale up the line thickness or stroke and expect it to look right. The light version of a font may be designed differently than the bold version.

For me, the key is that a font is designed to work as a family of glyphs. I don't think there is a minimum (or maximum) size for them. If it's too small to print (sub pixel), then it effectively doesn't exist.