New dialect and obsolescence in Hamaogi glottogram survey ― Dialect vocabulary change in 250 years ―

In this paper, we analyze the diffusion process of standard and dialectal forms in terms of geography and age distribution based on computational lexicology. The basic data are drawn from largescale questionnaire surveys. These surveys inquired about words recorded in the dialect glossary Hamaogi compiled 250 years ago in Tsuruoka City. MCA (Multiple Correspondence Analysis) was applied to the whole set of data. Eight words were described in detail on the basis of “age pillar maps” and “simplified glottograms”. Of the 406 words recorded in Hamaogi, many have been replaced by standard Japanese forms, and some by new dialect forms. But analysis of the data required us to additionally deal with the phenomenon of “obsolescence”. This is a process over 250 years by which words are forgotten and it applies to standard forms as much as dialect forms. The process of obsolescence seems to govern linguistic change, and even linguistic change in progress now may be influenced by obsolescence.