Definition of "conceptual"

The repeated exposure, over decades, to most taxa here treated has resulted in repeated modifications of both diagnoses and discussions, as initial ideas of the various taxa underwent—often repeated—conceptual modification.

1992, Rudolf M[athias] Schuster, The Hepaticae and Anthocerotae of North America: East of the Hundredth Meridian, volume V, New York, N.Y.: Columbia University Press, page viii