Informative site
In phylogenetics, informative site is a term used in the context of maximum parsimony, to refer to a characteristic that can usefully distinguish between samples at a genetic level. The informative site is a position in the relevant set of sequences at which there are at least two different character states at that point in the sequences, and each of those states occurs in at least two of the sequences. Character states can take on multiple types of data, including morphological or molecular information such as sequences of DNA or proteins.