I think I understand that an expressed antecedent is the word or set of words, actually stated, which provide meaning to a pronoun or pro-form. That is, the pronoun or pro-form refers to the same entity as was referred to by the antecedent.
However, how exactly do we define an unexpressed antecedent? Is it any possible word or set of words which, following the parameters of the context, could be inserted into the sentence(s), such that the pronoun or pro-form would refer to the same entity?
For example, in: 'I do not know who lives next door', we could say that the pronoun 'who' refers to the same entity as would the words, 'the person', or 'the individual', etc., in which case the unexpressed antecedent is actually one among many possible but unstated parts of speech.
Is this how the concept is usually defined, or am I overlooking something else?
Thanks for your help!