Graphene was defined [7] by H-P Boehm in 1986, and the nomenclature was officially adopted [23] by the International Union of Pure and Applied Chemistry (IUPAC) in 1994. It reads as follows:"Graphene is a single carbon layer of the graphite structure, describing its nature by analogy to a polycyclic aromatic hydrocarbon of quasi infinite size. Previously, descriptions such as graphite layers, carbon layers or carbon sheets, graphite monolayers have been used for the term graphene. Because graphite designates that modification of the chemical element carbon, in which planar sheets of carbon atoms, each atom bound to three neighbors in a honeycomb-like structure, are stacked in a three-dimensional regular order, it is not correct to use for a single layer a term which includes the term graphite, which would imply a three-dimensional structure. The term graphene should be used only when the reactions, structural relations or other properties of individual layers are discussed." Consistent with this definition, "graphite" should be used when graphene layers are stacked in the graphitic (Bernal) structure (see Figure 1), so that "few layer graphene" is incorrect and should be referred to as "thin graphite".In practice, graphene (including transferred graphene) is usually supported on a substrate. The term "freestanding graphene" is often used to suggest the absence of substrate-induced perturbations. Some even have suggested [24] to redefine graphene accordingly: "Graphene is a single atomic plane of graphite, which-and this is essential-is sufficiently isolated from its environment to be considered freestanding".However in practice graphene on a substrate is never freestanding. Substrates always affect the properties and quite significantly so in graphene transferred on SiO2 using the "Scotch tape" method, making this alternative definition ineffective. It makes more sense to adhere to the IUPAC definition of graphene and to apply "quasifreestanding" relative to a property. For electronic properties, quasi-freestanding implies that the electronic properties are essentially identical to those of an ideal graphene sheet. A recent publication in the authoritative journal Carbon suggests the usage of more precise definitions [25].The adhesion of graphene to many substrates involving van der Waals forces and/or electrostatic forces usually minimally affects its chemical and electronic properties (see below). But the adhesion to the substrate can be strong, involving significant chemical bonding of the carbon atoms in the graphene layer to the substrate. In these cases the electronic structure (as well as planarity) will be significantly modified. Finally, graphene can also be functionalized, in which cases atoms or molecules are chemically bound to graphene carbon atoms, whereby the electronic structure is typically significantly modified. Consequently chemical functionalization and chemical bonding to a substrate are closely related. Below, examples of all three forms of graphene are presented in the context of epitaxial...