Commas After Introductions // Purdue Writing Lab
https://owl.purdue.edu/owl/general_writing/punctuation/commas/commas_after...Introductory clauses start with adverbs like after, although, as, because, before, if, since, though, until, when, etc. Introductory phrases Phrases don't have both a subject and a verb that are separate from the subject and verb in the main clause of the sentence.