hrant asks us to cooperate in arriving at some definitions:
... Some terms are
not worth trying to pin down, but others ...
are. I think we would be doing great work if we could -at least
in the confines of Typo-L, and hopefully elsewhere subsequently-
define "legibility", "readability" and, yes, "decipherability"
(which I've come to realize is also needed).
i'd like to toss in one more term, just to be able to exclude it,
and tighten the boundaries: intelligibiliity.
someone said that "readable" referred to texts; i think that's
partly true (i've just finished reading max frankel's autobiography,
which is very highly readable in that sense, with typography that
didn't get in the way), but i think hrant's take on the readability
of type is also on the mark.
on the other hand, "intelligible" means i can make sense of what
i read. for example, i find well-composed mathematics, outside
of certain limited areas, both legible and (sometimes) readable,
but hardly intelligible. (i guess that "decipherability" comes
into this too. i hope i haven't muddied the waters too much here.)