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This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Stemmatics, stemmology or stemmatology is a rigorous approach to textual criticism. Karl Lachmann (1793–1851) greatly contributed to making this method famous, even though he did not invent it. The method takes its name from the word stemma. The Ancient Greek word στέμματα and its loanword in classical Latin stemmata may refer to "family trees". This specific meaning shows the relationships of the surviving witnesses (the first known example of such a stemma, albeit with the name, dates from 1827). The family tree is also referred to as a cladogram. The method works from the principle that "community of error implies community of origin." That is, if two witnesses have a number of errors in common, it may be presumed that they were derived from a common intermediate source, called a hyparchetype. Relations between the lost intermediates are determined by the same process, placing all extant manuscripts in a family tree or stemma codicum descended from a single archetype. The process of constructing the stemma is called recension, or the Latin recensio.
Output:
What is stemmatics?