As nouns the difference between abscess and ab

is that abscess is a cavity caused by tissue destruction, usually because of infection, filled with pus and surrounded by inflamed tissue {{defdate|first attested in the mid 16^th century}}{{reference-book | last =| first = | authorlink = | coauthors = | editor =brown, lesley | others = | title = the shorter oxford english dictionary | origdate = | origyear = 1933| origmonth = | url = | format = | accessdate = | accessyear = | accessmonth = | edition = 5th | date = | year =2003| month = | publisher =oxford university press | location =oxford, uk | language = | id = | doi = | isbn =978-0-19-860575-7 | lccn = | ol = | pages =8| chapter = | chapterurl = | quote =}} while ab is {{context|informal|lang=en}} abdominal muscle {{defdate|mid 20^th century}}{{reference-book | last =| first = | authorlink = | coauthors = | editor =brown, lesley | others = | title = the shorter oxford english dictionary | origdate = | origyear = 1933| origmonth = | url = | format = | accessdate = | accessyear = | accessmonth = | edition = 5th | date = | year =2003| month = | publisher =oxford university press | location =oxford, uk | language = | id = | doi = | isbn =978-0-19-860575-7 | lccn = | ol = | pages =2| chapter = | chapterurl = | quote =}} or ab can be {{context|slang|lang=en}} an abscess caused by injecting an illegal drug, usually heroin or ab can be {{context|us|lang=en}} the early stages of; the beginning process; the start.

As a verb abscess

is {{context|intransitive|lang=en}} to form a pus filled cavity typically from an infection.