A subself or subpersonality is a dynamic component of an individual’s psyche, having a distinctive perspective, value orientation, and “personality” of its own; that may be more or less dominant in the individual’s responses at any particular time; that the individual may be more or less conscious of, more or less accepting and benevolent toward; that may be more or less integrated into the individual’s total psychological system; and that is capable of growth and change over time. (I call a subself “dynamic” because it actively interacts with other components of the psyche and is not merely a passive repository of attitudes.)
The child-self is the component of the psyche containing the “personality” of the child one once was, with that child’s range of values, emotions, needs, and responses; not a generic child or universal archetype, but a specific, historical child, unique to an individual’s history and development. (This is very different from “the child ego-state” in Transactional Analysis; TA uses a generic model.)