In English grammar, a declarative sentence is a sentence in the form of a statement—in contrast to a command (imperative), a question (interrogative), or an exclamation (exclamatory). Declarative sentences are the most common type of sentence in the language. Also called a declarative clause.
Imperative verbs are verbs that create an imperative sentence (i.e. a sentence that gives an order or command). When reading an imperative sentence, it will always sound like the speaker is bossing someone around. Imperative verbs don’t leave room for questions or discussion, even if the sentence has a polite tone.
Interrogative Adverbs Can Also Be Used at the Head of Noun Clauses A noun clause is a clause that plays the role of a noun. Often, a noun clause will start with one of the so-called "wh"-words (e.g., what, who, which, when, where, why), a group which includes the interrogative adverbs.