Need to explain first argument of phrase/2 better

[Anniepoo]

Two other remarks regarding phrase/2:
You write:
To execute a grammar rule, we use Prolog's built-in phrase/2 predicate.
The first argument is a DCG body.
phrase(Body, Ls) is true iff Body describes the list Ls.

BUT that first argument is the HEAD of the/a “top" rule of a DCG, isn’t it?
(It can be the head of a lower rule too of course, if you want to test/find
substructures of a DCG.)

Maybe it’s clearer to replace "iff Body describes” with "iff (sub)DCG describes”?