substantiivilause

Substantiivilause is a dependent clause that functions as a noun within a larger sentence. It is commonly referred to in English-language grammar as a noun clause or content clause. A substantiivilause expresses a proposition, a question, or other content that can occupy noun-like positions such as subject, object, or complement.

The functions of a substantiivilause include acting as the subject of a sentence, as in That she arrived surprised us; as the direct object of a verb, as in I believe that he lied; as the object of a preposition, as in I am aware of what she did; and as a subject or complement, as in The idea is whether we should go. Substantiivilause clauses can be finite and introduced by complementizers such as that, whether, if, who, what, or where, or they can be formed with wh- words (what, where, why) and may appear with or without an overt introducer in different languages.

In English, the that is often optional: I think you are right or I think that you are right both represent substantiivilause usage. Other languages have dedicated conjunctions or particles to introduce these clauses, and some rely on inflection or word order rather than a separate word to mark the clause as a content clause. The underlying distinction is between clauses that rename or report propositions (noun clauses) and other subordinate clauses such as relative or adverbial clauses.

Cross-linguistic variation exists in how noun clauses are formed, whether they allow certain fronting or wh-movement, and how they interact with negation, tense, and modality. Substantiivilause is a central concept in the study of syntax and discourse, reflecting how speakers encode propositions and questions within larger sentences. See also content clause, complement clause, wh-question, and reported speech.