A conjunctive adverb, adverbial conjunction, or subordinating adverb is an adverb that connects two clauses by converting the clause it introduces into an adverbial modifier of the verb in the main clause.
[1] Some examples containing conjunctive adverbs are: The clause that a conjunctive adverb introduces invariably modifies a (usually previously expressed) logical predication.
Specific conjunctive adverbs are used to signal and signify purpose or reason (so that), sequence (then, since), exception (though), and comparison (whereas).
Some common English conjunctive adverbs are: Conjunctive adverbs are preceded by a semicolon or a period (full stop).
"The Mayfield Handbook of Technical & Scientific Writing".