In the UK a definition of leather is set out in the British Standard Glossary of Leather Terms (BS 2780) and this definition is used as a guide in applying consumer protection legislation such as the Sale of Goods Act and the Trade Descriptions Act.
In short, if a product is made from reconstituted leather fibres or if the surface coating is too thick then it cannot be sold as ‘leather’.
Hide or skin with its original fibrous structure more or less intact, tanned to be imputrescible. The hair or wool may or may not have been removed. It is also made from a hide or skin that has been split into layers or segmented either before or after tanning.
Note 1: If the leather has a surface coating, the mean thickness of this surface layer, however applied, has to be 0.15mm or less.
Note 2: If the tanned hide or skin is disintegrated mechanically and/or chemically into fibrous particles, small pieces or powder and then, with or without combination of a binding agent, is made into sheets or forms, such sheets are not leather.
This is the best definition of leather you will find. Leather is not an umbrellas term in that way that plastic and textile covers many chemically different materials from a wide variety of origins, some natural and some man made. Leather has only one origin type, which is what makes it so uniquely special.
Sometimes we are told we are too possessive of the naming, and I imagine this will be an ongoing argument. One problem is that many of the uses of leather as a terms have in fact been clear “abuses” where plastics or other materials are presented as “leather” with the deliberate intention of passing off, or of confusing the consumer. Equally consumers have an understanding of what to expect of leather and become rightly angry when their sofa needs repairing, only to be told that the material is not leather and cannot be mended.
Leather needs to evolve as it always has done as its end uses have changed of over time. And there will never be enough leather for every end use, so there will always be competitors. The tanning industry can have no complaint with that, and with battling head on against competitive materials.
I would also argue that we need to be much more open to working with new materials, and with hybrids. That way we can influence the naming, but more importantly expand our technical skills into adjacent areas, be involved in creating some new market opportunities, and perhaps use some of our trimmings or shavings etc to build really clever hybrid materials.
Why limit ourselves too much, in this modern age?