Stimulus Class refers to a group of stimuli that share a set of common features or characteristics and evoke similar responses. The stimuli within a class can vary in form but are grouped together because they serve the same function or produce the same behavioral response.
Example
A group of different chairs (e.g., an office chair, a dining chair, and a rocking chair) can all be part of the same stimulus class because they all serve the function of being sat on. Despite their differences in appearance, they evoke the same response—sitting.