Final answer:
Perceptual regions differ from formal and functional regions in that they are based on subjective perceptions and opinions rather than objective, measurable data.
Step-by-step explanation:
An important characteristic that distinguishes perceptual regions from formal and functional regions is that perceptual regions are based on subjective feelings and opinions of people, rather than objective, measurable data.
Perceptual regions, sometimes also known as vernacular regions, are informed by the experiences, cultures, and ideas of those who reside in or interact with the region.
Unlike formal regions with defined governmental or administrative boundaries, or functional regions with a defined economic or functional connection (such as a metropolitan area with a central city and its suburbs), perceptual regions are shaped by the perceptions and cognitive maps of individuals.
For example, the term 'The South' in the United States may represent a perceptual region whose boundaries vary depending on whom you ask, influenced by factors like state identity, cultural practices, or historical context.