American English

Definition of boundary noun from the Oxford Advanced American Dictionary



    (pl. boundaries)
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  1. 1a real or imaginary line that marks the limits or edges of a place or piece of land national boundaries county boundaries boundary changes/disputes The fence marks the boundary between my property and hers. He could just see her beyond the boundary wall of the cemetery. Thesaurusborderboundary frontier barrierThese are all words for a line that marks the edge of something and separates it from other areas or things.border the line that separates two countries or areas; the land near this line:a national park on the border between Montana and Wyomingboundary a line that marks the edges of an area of land and separates it from other areas:The fence marked the boundary between my property and hers.border or boundary?The point where you cross from one country to another is usually called the border. The line on a map that shows the border of a country can be called the boundary, but “boundary” is not used when you cross from one country to another:After the war, the national boundaries were redrawn. Thousands of immigrants cross the boundary every day.Boundary can also be a physical line between two places, for example between property belonging to two different people, marked by a fence or wall:the boundary fence/wall between the propertiesfrontier the border between two countries or areas; a line that marks the beginning of an unexplored or dangerous area:the frontier between Guatemala and Mexico The Ingalls family crossed the frontier in a covered wagon.barrier something that exists between two places and prevents easy movement between them:The mountains form a natural barrier between the ocean and the desert.Patterns across/along/on/over a/the border/boundary/frontier/barrier at the boundary/frontier/barrier the border/boundary/frontier with a place the northern/southern/eastern/western border/boundary/frontier a national/common/disputed border/boundary/frontier
  2. 2an imaginary line that marks the limits of something and separates it from other things the boundary between acceptable and unacceptable behavior to extend the boundaries of high art to include some popular music
  3. 3[usually plural] the farthest limit of something; the limit of what is possible or acceptable Scientists continue to push back the boundaries of human knowledge. how to set boundaries with your teenager to violate the boundaries of a professional relationship
See the Oxford Advanced Learner's Dictionary entry: boundary

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