Key difference: Essentially, a spirit is the spark of light, the living force in the body. It is the reason why we are living and moving around. It is the source of power and control for both your body and soul. When we die, the spirit i.e. living force leaves the body, hence the body dies. The spirit stops existing, while the soul moves on. A ghost, on the other hand, is someone who has passed on and is "stuck" between the physical world and the afterlife.

The terms soul and ghost are often used interchangeably. Most people are sure what the difference between the two words is. In order to find out, let first see the definition of the two words. This might also interest you: Holy Ghost Vs. Holy Spirit.  

Dictionary.com defines ‘spirit’ as:

• The principle of conscious life; the vital principle in humans, animating the body or mediating between body and soul.
• The incorporeal part of humans: present in spirit though absent in body.
• The soul regarded as separating from the body at death.
• Conscious, incorporeal being, as opposed to matter: the world of spirit.
• A supernatural, incorporeal being, especially one inhabiting a place, object, etc., or having A particular character: evil spirits.
• A fairy, sprite, or elf.
• An angel or demon.

“Ghost’ is defined as:

• The soul of a dead person, a disembodied spirit imagined, usually as a vague, shadowy or evanescent form, as wandering among or haunting living persons.
• A mere shadow or semblance; a trace: He's a ghost of his former self.
• A remote possibility: He hasn't a ghost of a chance.
• (Sometimes initial capital letter ) a spiritual being.
• The principle of life; soul; spirit.

Also see: Ghost Vs. Devil 

Essentially, a spirit is the spark of light, the living force in the body. It is the reason why we are living and moving around. It is the source of power and control for both your body and soul. When we die, the spirit i.e. living force leaves the body, hence the body dies. The spirit stops existing, while the soul moves on.

However, sometimes if one dies the spirit might still linger on in the physical world or come back from the afterlife from time to time. It may do this in order to watch their loved one or to keep an eye on them to make sure that they are doing well.
Also see: Ghost Vs. Vampire 

A ghost, on the other hand, is someone who has passed on and is "stuck" between the physical world and the afterlife. This might be because they died before it was their time to and/or they died a violent death. For example, in an accident, or perhaps they were murdered. In such a case, the person tends to be stuck in the physical world. They do not cross through the light to go on to the afterlife. They stay in this netherworld. Sometimes, they may not even realize that they are dead and may go on about their lives as they would if they were still alive.

Furthermore, a spirit can also be used to refer to a fairy, sprite, elf, angel or demon. Spirit is a versatile word, which had come to mean many things over the eons. 

Also see: Ghost Vs. Witch

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