An interrogative pronoun realises the position of a verb argument or of a subordinate sentence in the clause in which it occurs. It enables an expansion E which contains an instantiation of X as answer to the main clause P where X occurs. If it introduces an indirect question, the indirect question realises the position of a syntactic construction which depends on certain verbs such as `demander'.
Test:
Given X a pronoun, P the clause in which X occurs: If X enables an expansion E and if E contains an instantiation of X in P, then X is an interrogative pronoun.
Examples:
Test:
Given X a pronoun, P a main clause in which X
occurs,
the clause introduced by X: If X realises a verb argument of
or
a subordinate clause,
and if
is a syntactic construction of a certain verb occuring in P, such as `demander', then X is an interrogative
pronoun (which introduces an embedded interrogative sentence).
Examples:
Interrogative pronouns can introduce direct or indirect interrogative sentences:
Interrogative pronouns can introduce infinitive sentences: