boundary boundary /ˈbaʊndri/

noun

1. () The line or plane indicating the limit or extent of something  ( bound , bounds , boundary )
   the line or plane indicating the limit or extent of something
     They crossed the boundary between two states and entered a new jurisdiction.
   They crossed the boundary between two states and entered a new jurisdiction.
   
2. () A line determining the limits of an area  ( bound , boundary , edge )
   a line determining the limits of an area
   
3. The greatest possible degree of something  ( bound , boundary , limit )
   the greatest possible degree of something
    What he did was beyond the bounds of acceptable behavior
   what he did was beyond the bounds of acceptable behavior
    To the limit of his ability
   to the limit of his ability