As well, diffusion means that some common features may have spread beyond their original starting point through contact, and as a result, a number of characteristics occur in a language assigned to a proposed subgroup, but the same feature is also found in other adjacent languages that are not analyzed as part of the subgroup in question. Appeal to both genetic subgroups and areal diffusion is required. Goddard notes: "Each Eastern Algonquian language shares features with each of its immediate neighbors, and the resulting continuum is of a sort that is likely to have resulted from the spread of linguistic innovations among forms of speech that were already partly differentiated but still similar enough to make partial bilingualism easy."