As adverbs the difference between certainly and absolutely
is that
certainly is in a way which is certain; with certainty while
absolutely is in an absolute or unconditional manner; utterly, positively, wholly {{defdate|first attested around 1350 to 1470}}
[{{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 =9| chapter = | chapterurl = | quote =}}].
As a interjection absolutely is
yes; certainly; expression indicating strong agreement {{defdate|first attested around 1350 to 1470}}
[.
]