A shadow is the dark shape cast when a body blocks light — and, in psychology, often a reference to the 📝Shadow Self: the disowned parts of a person kept out of conscious view.
The word comes from Middle English shadwe and Old English sceadwe, an inflected form of sceadu, "shade," so shadow stands to shade as meadow stands to mead. Its literal sense is the image of darkness an object throws, but the figurative senses arrived early: by the thirteenth century a shadow could be anything unreal or insubstantial, by the fourteenth a ghost, and later whatever follows a person closely. A shadow is also a faint trace (not a shadow of doubt), a gloom over something, and, as a verb, to follow unseen.
Shadow differs from shade, which names an area sheltered from light rather than the shape a particular object casts. In 📝Jungian Psychology the word took on a technical meaning: 📝Carl Jung used it for the parts of the personality the conscious ego refuses to recognize as its own, which then appear projected onto other people. Because those contents sit in the 📝unconscious, Jung held that wholeness requires integrating the shadow rather than suppressing it, and that a person who has not done so tends to project unresolved material onto those they try to help, an idea collected in 📝Accept Yourself Before Helping Others.
I mostly use shadow in Jung's sense. In the 📝Consciousness Gap I describe founders and creatives who have done the work of integrating their shadow, and the 📝Soul Core image treats shadow as material for transformation rather than a fault to burn away.