Occultism is the study of occult or hidden wisdom. To the occultist it is the study of "Truth", a deeper truth that exists beneath the surface: 'The truth is always hidden in plain sight'. It can involve such subjects as magic (alternatively spelled and defined as magick), alchemy, extra-sensory perception, astrology, spiritualism and numerology.
The word occult comes from the Latin word occultus (clandestine, hidden, secret), referring to "knowledge of the hidden". In the medical sense it is used to refer to a structure or process that is hidden, e.g. an "occult bleed" may be one detected indirectly by the presence of otherwise unexplained anaemia
Some religious denominations view the occult as being anything supernatural or paranormal which is not achieved by or through God, and is therefore the work of an opposing and malevolent entity. The word has negative connotations for many people, and while certain practices considered by some to be "occult" are also found within mainstream religions, in this context the term "occult" is rarely used and is sometimes substituted with "esoteric".