Adult is the fourth level of Digimon development. All Digimon will achieve this level naturally, so long as they survive long enough; further evolution requires special processes of data intake and refinement. Adult-level Digimon will eventually die of old age if they do not evolve further, but their lifespan may reach that of a human's or extend even further, depending on various factors.
Digimon of the Adult-level are the most visibly, prominently common in the Digital World. They vary wildly in size, shape, and ability; their personality and intellect are fully developed at this level, and are also extremely diverse.
As individuals, Digimon of the Adult-level also vary much more freely in size than those of the Child-level. "Typical Size" given is average, but individuals may be significantly smaller or larger than that average. Because Digimon may remain at the Adult-level for many years, there are also great power discrepancies between individuals based on training and experience.
For Digimon under the care of a Tamer, the Adult-level form is the one typically used in combat and physical tasks, if they have not already naturally evolved past the Child-level. It is the simplest feat of Jump Evolution to perform, requiring only basic synchronization between a Tamer and Digimon.