As a supplement to Martha's comment (quoted below) that in a sentence like "The pain
is in her foot," the phrase "in her foot" is adverbial: True enough, but there is
more than one kind of adverbial prepositional phrase that can occur in a sentence
with a linking verb.  Take the sentence "The fans were in the stands during the
game."   Here "in the stands" is an adverbial that is a complement; on the other
hand, "during the game" is a standard verb-phrase abverbial and not a complement.
Notice that you can say, "The fans were in the stands," but you can't say, "The fans
were during the game."  The two adverbial prepositional phrases are doing different
things.  Linking verbs require complements, and adverbials can be complements, just
as noun phrases and adjectival phrases can be complements, but a linking-verb
sentence can also have an adverbial that is not a complement.

Dick Veit

Martha Kolln wrote:

> . . .  And in the case
> of "The migraine is in her head," "be" can take an adverbial as well as a
> subject complement.  The pain is in her foot, The book is in the library,
> My mother is in the hospital, The play was yesterday.  Those structures
> following "be" are adverbial, not adjectival.  You might want to call them
> complements, in that they "complete" the predicate--but they're not
> adjectival.