The unit of change
Language shift is a change in a community’s habitual language use across generations or social settings. It is not a single event shared by every speaker. A family may keep one language at home while using another in a market, school or court; a later generation may use the latter in both places. The question is therefore not simply “When did language A disappear?” but “Which people used which languages, with whom, for what work, and at which dates?” State the population and domain before proposing a historical transition.
A language can gain a new role while losing another. Sumerian’s spoken use declined, yet scribes continued to teach, copy and interpret it. Latin developed into regional Romance vernaculars and also remained a learned written language. These are different histories from an immediate replacement by an unrelated language. A change in administrative language, script or literary register may accompany shift, but none is itself a measurement of what children learned at home.
Four distinctions
Maintenance means continued use within a domain or across generations. Replacement means that one language takes over a specified function previously served by another. Language change means that a continuing speech tradition develops new forms; it need not involve replacement by a different language. Written survival means that texts keep being produced, copied or read; it need not imply native speakers. These distinctions can overlap in one place and century, so an account must track them separately.
Avoid a false binary between “alive” and “dead.” A ritual language may no longer be acquired as a home language but still be actively studied, pronounced and composed. A vernacular may be vigorous among speakers and almost absent from surviving manuscripts. Labels should describe the evidence, not rank the worth of a community or treat its choices as inevitable.
Evidence and inference
A dated legal decree establishes a language of legal publication. A household letter establishes at least the language practice of its writer, addressee or scribe. A bilingual school exercise establishes a teaching context. None alone gives a population-wide percentage of home speakers. To strengthen a historical inference, assemble records of several genres and places, distinguish originals from later copies, and compare the dates at which each domain changes.
Practice: take the statement “Greek replaced Egyptian in Egypt.” Rewrite it as three testable claims about administration, private writing and spoken transmission, each with its own date range and needed sources. The exercise may end with “unknown” for the speech question. That is a stronger conclusion than assigning a convenient date to a process the archive cannot directly measure.
Modern-language examples on this page clarify a linguistic pattern. They do not establish unattested sounds or forms for an ancient language. Follow the cited sources below and keep editorial readings separate from the surviving trace.