Common examples of essential characteristics include intensity of development (from rural to suburban to urban) and building use (church, hospital, school, apartment, house, etc.)
Non-essential characteristics are those which, if modified, would not change the building type.
Color, for example, would rarely be considered an essential characteristic of building type.
In architecture and urban planning discourse, typology is sometimes distinguished from morphology, which is the study and classification of buildings according to their shape or form (gk.
This distinction is particularly relevant in urban planning and design, where some have begun to question the standard model of single-use zoning codes in favor of form-based zoning codes that regulate development not by use (commercial, residential, industrial, etc) but instead by the shape, size, and placement of buildings on their lots.