This a reply to the same question in 2003 on here
Metandienone
Metandrostenolone
NSC-42722
Métandiénone
Dehydromethyltestosterone
Metandienonum
Methandrostenolone
....are all SYNONYMS for Methandienone.
I believe originally, the way that at particular company
made the drug influenced the name that they used.
ie: alkylation of the 17-carbon = Methandienone
esterification of the 17-OH group = Methandrostenolone
modification of the steroid nucleus = Dehydromethyltestosterone
but chemically, all the above are 17beta-Hydroxy-17alpha-methylandrosta-1,4-dien-3-one. ( C20 H28 O2 )