Dramatis Personae

Definition of dramatis personae
(a): the characters or actors in a drama.
(b): a list of the characters or actors in a drama.

Definition of gradient
(a): 
an inclined part of a road or railway; a slope.
(b): an increase or decrease in the magnitude of a property (e.g., temperature, pressure, or concentration) observed in passing from one point or moment to another.
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