BOUNDARY -is the border of an area or the limit -something that indicates or fixes a limit or extent
CONSTRAIN -is a restriction or limitation
-to hold back by
-To keep within close bounds INTERFACE - is the place at which independent and often unrelated systems meet and act on or communicate with each other -The point of interaction or communication between a computer and any other entity, such as a printer or human operator. -The word was applied to other interactions as well—between departments in an organization, for example, or between fields of study. Shortly thereafter interface developed a use as a verb, but it never really caught on outside its niche in the computer world, where it still thrives. -a surface forming a common boundary of two bodies -the place at which independent and often unrelated systems meet and act on or communicate with each other INTERRELATIONSHIP -is to bring into mutual relation or to have mutual relationship -mutual or reciprocal relation or relatedness; "interrelationships of animal structure and function" -the greatest possible degree of something; "what he did was beyond the bounds of acceptable behavior"; "to the limit of his ability" ** they are different depending on their uses, or how it is applied.