Legibility or Readability is it?

On these pages I use the terms Readability and Legibility pretty-much interchangeably. Strictly, legibility should mean you can read it, and readability that you can read it and understand it or feel comfortable with it, I think that’s right anyway, it being what some people maintain, for example see the Wikipedia page on Typography.

On this basis, if you don’t speak any English then for you this page is legible, but not readable.

And more relevent to these pages, a block of text set in Microsoft’s Comic Sans font in a smallish typeface (8pt) as in the leftmost example below is legibile:

     

But not what you’d call readable, certainly not if you can imagine that spread over a whole page, whereas the passage next to it (in Bookman Old Style 8pt) would on paper be both legible and readable, it doesn’t render so well on screen because of the thin letter shapes and serifs. The third example is Bitstream Vera font 8pt, the most readable of the three on screen, but would probably be less readable than Bookman on paper, in a passage of text of this type I must stress.

When we start talking about whether a block of text is readable or legible in one colour over a second colour, then readability is possibly the better term, though this must be somewhat subjective, whereas legibililty is essentially more precise.

Anyway, that’s why I use the terms interchangeably. It isn’t that simple a matter when you come to actual examples, so I think it best not to try and be too precise about it.