Explain why a morbid expression of emotion is described as encompassing a specific, recognised set of individual patterns rather than being a single uniform sign.

It covers several distinct, individually recognised patterns, including blunting, incongruity, constriction, stiffening, lability, and incontinence of affect, each with its own specific quality and clinical associations. Grouping these together under one umbrella term while still distinguishing which specific pattern is present matters because each pattern can point toward a different underlying process or severity, even though they share the common defining feature of the patient's lack of insight into the change, usually first noticed by others rather than reported by the patient. Recognising both the umbrella feature, unawareness, and the specific pattern present therefore gives a fuller clinical picture than either alone.