My list of 51 things turns out to be 25 prefixes and their meanings. They are as follows:
A - not
Ab - away
Ad - increase
Ante- before
Be- completely
Com- with
Contra- against
De- down
Dia- accross
En- put into
Hemi- half
Hypo- under
Infra- below
intra- inside
Ob- blocking
Peri- round
Semi- partly
Sub- lower
Sym- in union
Ultra- bveyond
Un- not
Under- below
Op- against
Col- jointly
Abs- from