Final answer:
A surface marker that identifies a lineage or differentiation stage is a molecular marker, which may be a protein signature, a genetic marker, or a reflection of genomic or proteomic activity.
Step-by-step explanation:
A surface marker that identifies a particular lineage or differentiation stage is known as a molecular marker. These markers are essential in distinguishing different cell types in a variety of biological and medical fields, such as developmental biology and pathology. Molecular markers can be proteins, genes, or other molecules that are characteristic of specific cell types or stages of development. They may include protein signatures unique to a diseased state, genetic markers inherited from parents, or markers that reflect the activities of the genome or proteome within the cell or organism.