Just-noticeable difference (JND) refers to the smallest difference between two stimuli that can be detected by an observer. There are several synonyms for the term JND, such as difference threshold and sensory threshold. Difference threshold refers to the absolute threshold for detecting a difference between two stimuli. Sensory threshold, on the other hand, refers to the minimum amount of stimulation required for a particular sensory modality to register in human perception. Another synonym for JND is differential threshold. This term is used to describe the smallest change in stimulus intensity that can be detected by an observer. Regardless of the term used, JND is an important concept in sensory perception and helps to understand how people perceive differences in stimuli.