A verbal stimulus may have features that are non-verbal. For example, if you say “dog” very loudly and someone says “too loud,” the response “too loud” is not controlled by the pattern of the stimulus that results from your verbal behavior, but rather by a dynamic characteristic of that stimulus.
A physical energy change capable of affecting an organism’s sensory receptors that has the following features:
It has a specific form or pattern which, as a unit, has controlling effectiveness
It is the result of verbal behavior
Modality: auditory, visual, etc.
Dynamic characteristics such as size, intensity, etc.
Function: discriminative, reinforcing, punishing, etc.