Growth is change expressed in two fundamental ways:
(1) Existential increase in the size of an entity. This increase must be due to some dynamism inside the entity. Consider entity X and its containership Y. X has grown if and only if some dynamism inside X has caused X to increase in size. Y will also increase in association with X's growth. X has not grown if the increase in X's size is due solely to some dynamism external to X (e.g an external force stretches X).
(2) Existential increase in the number of occupants in a given container. The dynamisms responsible for this increase may be within the occupants, external to the occupants or both. The increase in the number of bacteria in a given space is an example of increase due to dynamism within occupants. Population increase due to migration into a given space is an example of increase due to external dynamism. Population increase due to both increase in birth rate of occupants in a given space and migration into the space, is an example of increase due to both internal and external dynamisms.
Some growths express both (1) and (2). For example, in human growth, human-cells divide to increase in number and aggregate to form the tissues and organs that cause the increase in size. Plant growth also expresses both (1) and (2).
Business growth is an example of non-biological growths that express both (1) and (2). Business executives use the cues from external dynamisms (markets, regulations, etc) to create internal dynamisms that increase the sizes of their businesses (more branches, more profits, more employees, etc). The increase in branches and employees expresses (2) while also being part of the expression of (1).
Abstract growth (growth in knowledge, growth in wisdom, spiritual growth) is the increase in the number of states of intellectual and spiritual improvement that, like the rungs of a ladder, takes an entity to the zenith of enlightenment.
The change expressed by growth; the space wherein growth unfolds; the work done to realize the growth; and the growing matter are all expressions of Pj Problems. Consequently, growth is an expression of Pj Problems.