An apparition is generally described as a ghost of a deceased person. However, the formal definition is ‘the act of becoming visible.’
An Apparition is a Spirit who has become visible.
An apparition can take many forms to become visible, including, but not limited to:
White or black smoke
A translucent energy mass
Light flashes or orbs
A face or a face shape
A semi-translucent whitish person shape
A full-color person with slight translucence
The visible nature of a Spirit depends on many things.
While ghost movies would have you believe apparitions always appear as whitish human figures - this is rarely the case.
What a Spirit looks like when it appears, largely depends on a variety of intermingling factors, including, but not limited to:
What the Spirit knows how to do
The amount of energy present in the space
The number of other Spirits in that space using the available energy
How they think they can appear
How long they have been dead
How closely tied they are to the physical plane
What your abilities to see and notice Spirits are
How fearful you are of seeing a Spirit
When a Spirit becomes visible (becomes an apparition) the goal is to be seen by someone, generally, with the least amount of energy put forth as possible.
If a Spirit is still learning how to come through, or they would like to appear, but want to allocate their available energy to do other things - like provide you with clairaudient messages - they may not be as blatantly visible as you may think or expect, because they are choosing to allocate their energy for other, more ‘important’ purposes.
If you see an Orb of light, a clear dense mass or a wisp of black smoke - take a moment to consider - that this may be a Spirit appearing and they’re doing their best to be seen by you.