Conjunct adverbials are words and phrases that express textual relationships. Conjunct adverbials serve to link clauses.
Conjunct adverbial is a grammatical function.
The grammatical forms that can function as the conjunct adverbial in English grammar are the adverb phrase and prepositional phrase.
Conjunct adverbials are not constituents of either the subject or the predicate.
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.