Here is S-1's chemical structure:
3-(4-Fluorophenoxy)-2-hydroxy-2-methyl-N-[4-cyano-3-(trifluoromethyl)phenyl]-propanamide
Here is Ostarine's chemical structure:
((2R)-3-(4-cyanophenoxy)-N-[4-cyano-3-(trifluoromethyl)phenyl]-2-hydroxy-2-methylpropanamide)
Similar because all sarms are close in structure but not the same.