The official record of the historical descent of dharma teachings from one teacher to another; by extension, may refer to a tradition. A lineage in Buddhism is a line of transmission of the Buddhist teaching that is "theoretically traced back to the Buddha himself." The acknowledgement of the transmission can be oral, or certified in documents. Several branches of Buddhism, including Zen and Tibetan Buddhism maintain records of their historical teachers. These records serve as a validation for the living exponents of the tradition.
The historical authenticity of Buddhist lineage is questionable. Stephen Batchelor has claimed, speaking about specifically Japanese Zen lineage, "the historicity of this “lineage” simply does not withstand critical scrutiny." Erik Storlie has noted that transmission "is simply false on historical grounds." Edward Conze said "much of the traditions about the early history of Ch’an are the inventions of a later age."
Example via www.ramdass.org: The Purpose of a Lineage