The dichotomy between functional and formal geography suggests the division of geography into the geography of real places and geography of geometric places in black and white.
The dichotomy came into being in order to avoid the division between regional/systematic and physical/ human geography.
The believers of functional regions argue in favour of a causal relationship between the complex and heterogenous features of a place as well as the causal relationships among phenomena at different places on the earth. So, the basic spatial idea suggests that phenomena such as relief, soil, land use, transport links and industrial clusters are arranged not by chance but according to a rational idea of using space in the best possible manner.
The homogenous regions formed by social groups and societies are called formal regions. These communities are organised into microsystems or part systems. A formal or uniform region represents a “discrete distribution” defined on the basis of certain specified criteria and has a homogenous character in terms of those criteria. Formal regions are defined on the basis of a single feature or a “well-defined association of several selected features”.
The functional or nodal region is defined on the basis of its area of influence around a nodal centre, that is, a city or a town or several nodal centres related to each other. The most important factor for delimiting the functional region involves the spatial interaction of a node with its hinterland.
In the study of functional regions, the issues related to absolute distances and space have little relevance. This approach considers the measurement of accessibility and isolations in terms of cost distance, mileage etc.
According to Pip Feror, since factors such as socio-economic demands and technological advancement affect distances in terms of cost or time, the space is truly dynamic in nature. Such space has been defined by Pip Feror as plastic space, i.e., a space that changes continuously in size and form.
P.E. James has viewed such dichomies— including deductive versus inductive, topical versus regional, idiographic versus nomothetic—as mutually exclusive rather than contradictory in nature.