The Image of the City Theory, Kevin Andrew Lynch, from the book of “ Image of the City “ (MIT Press, 1960)

• Paths are the channels along which the observer, customarily, occasionally, or potentially moves. Paths are the streets, sidewalks, trails, and other channels in which people travel
• Edges are the linear elements not used or considered as paths by the observer. Edges are perceived boundaries such as walls, buildings, and shorelines;
• Districs are the medium to large section of the city, conceived of as having two dimensional extent. Districts are relatively large sections of the city distinguished by some identity or character;

• Nodes are points, the strategic spots in a city into which an observer can enter, and which are the intensive foci to and from which he is traveling. Nodes are focal points, intersections or loci; and
• Landmarks are another type of point of references, but in this case the observer does not enter within them, they are external. Landmarks are readily identifiable objects.

from the book of “ Image of the City “ (MIT Press, 1960)