the mind > language > linguistics > other schools of linguistics > [noun] > synchrony, diachrony, or panchrony
1959 W. Baskin tr. F. de Saussure i. iii. 81 Everything that has to do with evolution is diachronic. Similarly, synchrony and diachrony designate respectively a language-state and an evolutionary phase.
1963 9 54 The synchrony and diachrony of language are reflected in the synchrony and diachrony of grammatical theory.