1. An instance or prevalence of a selected sort or class: a case of mistaken id. See Synonyms at illustration. portfolio - a sizable, flat, slim case for carrying loose papers or drawings or maps; normally leather; "he remembered her for the reason that she was carrying a substantial portfolio" https://casestudywritingservice15529.blogolize.com/what-does-case-study-writing-help-mean-75437956