A child’s developmental trajectory that deviates from the normal and expected standards for his or her age in physical, psychological, cognitive or social aspects. This type of development is characterized by behaviors or abilities that are not appropriate for the child’s age, such as language delays, attention difficulties, impaired motor coordination, or problems with social interaction. Deviant development can result from a variety of factors, including neurological disorders, genetic disorders, traumatic brain injuries, or negative environmental and social influences such as emotional deprivation or lack of cognitive stimulation. This deviation is an indicator of potential problems in learning or the formation of higher mental functions and requires a thorough and comprehensive assessment to determine the cause of the deviation and its impact on the child’s overall development. A deep understanding of deviant development allows the development of comprehensive early intervention programs aimed at maximizing the child’s return to normal trajectory, while improving his cognitive, emotional and social abilities and minimizing the negative impact of deviation on his learning and adaptation to the environment.