Aniline leather is:

“Leather that has not received any coating of pigmented finish.”

In other words, the finish is completely transparent, so that the original grain surface can be seen through the finish completely unhindered by any pigment particles.

Semi-Aniline leather is defined by the ITC, IULTCS and ISO as:

“Leather which has been aniline dyed or stained, incorporating a small quantity of pigment, not so much as to conceal the natural characteristics of the hide.”

Explanatory Note: An analogous situation to semi-aniline leather is the treatment of a wooden household deck with a stain labeled “semi-transparent” on the container. Such stains contain just enough pigment to provide protection against fading, but not enough to completely obscure the surface, allowing the natural beauty of the wood grain to partially show through, while disguising minor defects and blemishes.

Pigmented Leather is:

"Leather whose surface has a finish containing pigment particles that render the finish completely opaque."(This is exactly the same as a “solid” finish used to protect external wooden structures, such as decks).