A lack of reality
“Abstraction” means to draw or pull away from, of removal, of isolation.
Abstract photography can therefore be where the subject is so captured that it no longer has an immediate association with the object world, it’s so removed from it’s inherent context, that meaning has to be sought and interpreted.
The subject can be so abstracted that it’s just a fragment of the original scene, but it can also be a distorted version of the original.
Colour, light, shadow, shape, texture, angle of view etc. are all used to create an image with an unreal appearance, to convey a feeling, sensation, emotion, or an impression.