Describing carbons

Carbon materials are unique materials for their diversity, owing to three possible hybridisation states (sp, sp², sp³), their ability to switch from one phase to another upon various external stresses (thermal, mechanical, pressure…), and the tolerance of graphene (sp²C) to defects of many kinds. This makes their description difficult, due to the lack of standardised vocabulary and misuses or ignorance of the existing ones. A common language is needed so that every word has the same meaning to everyone and that carbon scientists understand each other as accurately as possible. This paper aims to clarify the basic terminology to be used on this matter, by reminding some important definitions or terms, e.g. allotrope, polymorphism, molecular form, crystallite, graphitic, graphene, graphene layer, graphenic, graphitisation, graphitisation treatment..., based on authoritative publications when available. In addition, as sp²C-based carbon materials exhibit the largest variability, a four-term description scheme (namely: morphology, texture, nanotexture, structure) is proposed and argued, which is believed to be sufficient (and necessary) to describe any kind of carbons, but molecular forms. Applying the recommendations proposed is expected to bring more consistency, clarity, and understandability to the forthcoming literature dealing with carbon materials.