Look at the following examples:
The head-initialized antecedent (italicized) has a complementizer (bolded) that is the syntactic head of a full clause, the embedded clause (coloured amber).
The complementizer together with the embedded clause (coloured amber) can perform the role a complement, a subordinate clause that functions as the subject or the object of particular verbs. There can also be a relationship, called a filler-gap dependency, between a wh- complementizer and a gap:
SUMMARY/OBSERVATIONS: The first two sentences have a that-clause that functions as an appositive or what is known as an expletive because the that-clause does not serve a grammatical function. In the third sentence, there is a filler-gap dependency, wherein the wh- interrogative, or complementizer, introduces an embedded clause. The word what fills a gap created by the verb, i.e., to be what. And in the last sentence, the entire clause functions as a subject, i.e., She sipped what looked like orange juice.
[F]iller–gap dependency refers to a relationship between a filler, which is a wh- complementizer such as ‘what’ or ‘who’, and a gap, which is an empty syntactic position licensed by the filler.Wilcox, Ethan, et al.Wilcox, Ethan, et al. “What Do RNN Language Models Learn about Filler-Gap Dependencies?: Semantic Scholar [PDF].” Undefined, 21 Aug. 2018, … Continue reading
|↑1||Wilcox, Ethan, et al. “What Do RNN Language Models Learn about Filler-Gap Dependencies?: Semantic Scholar [PDF].” Undefined, 21 Aug. 2018, www.semanticscholar.org/paper/What-do-RNN-Language-Models-Learn-about-Filler-Gap-Wilcox-Levy/461297186f25a51d96b52b4f5f04b03e0bed476e. Accessed 26 Feb. 2020.|