[1] (The word adverbial itself is also used as an adjective, meaning "having the same function as an adverb".)
Many types of adverbials (for instance: reason and condition) are often expressed by clauses.
This may be performed by an adverb or a word group, either considered an adverbial: for example, a prepositional phrase, a noun phrase, a finite clause or a non-finite clause.
[example needed] Often ignored, expletives may take up many adverbial syntactic functions.
Pragmatically and semantically, they often serve as intensifiers, boosting the content of the clause they appear in.