It later acquired the meaning of 'although', indicating a concession on the part of the speaker ("While it could use a tune-up, it's a good bike.").
[4] In Traugott's view, subjectification is a semasiological process in which a linguistic element's "meanings tend to become increasingly based in the speaker's subjective belief state/attitude toward the proposition".
[4][1] From Langacker's standpoint, "an expression's meaning always comprises both subjectively and objectively construed elements, and it is individual conceptual elements within an expression's meaning that, over time, may come to be construed with a greater degree of subjectivity or objectivity".
[5] Traugott and Dasher schematize the process of subjectification elsewhere in the following cline: non-subjective > subjective > intersubjective[5]Grammaticalization is an associated process of language change in which "lexical items and constructions come in certain linguistic contexts to serve grammatical functions, and once grammaticalized, continue to develop new grammatical functions".
[4] As shown in the cline above, subjectification is theorized to be a unidirectional process; in other words, meanings tend to follow the path from left to right and do not develop in the reverse direction.