As adjectives the difference between retaining and retentional
is that retaining is of or pertaining to something that retains something else, as with a retaining wall while retentional is of or pertaining to retention.
As a verb retaining
is present participle of lang=en.
retaining
English
Adjective
(-)
Of or pertaining to something that retains something else, as with a retaining wall.
Verb
(head)