Mild cognitive impairment (MCI) is a transitional state between normal aging and early dementia, characterized by cognitive deficits that do not meet the criteria for dementia. It has been proposed as a diagnostic entity to identify individuals at risk of developing Alzheimer's disease (AD). MCI is associated with an increased risk of progression to dementia, particularly AD, and is classified into subtypes based on the cognitive domains affected. The diagnostic criteria for MCI include subjective memory complaints, objective memory impairment, preserved general cognition, normal activities of daily living, and not being demented. The concept of MCI has been refined over time, with various studies highlighting its role in predicting dementia progression. MCI is often distinguished from normal aging and early dementia, though the boundaries can be subtle. Research has shown that MCI can be unstable over time, with some individuals reverting to normal cognitive function. The diagnosis of MCI is challenging due to the lack of strict criteria, but it is considered a clinically useful entity. The application of MCI criteria is similar to those used for dementia and AD, with a focus on cognitive impairment rather than full dementia. The classification of MCI subtypes, such as amnestic MCI (a-MCI) and multiple domain MCI (md-MCI), helps in predicting the likelihood of progression to different forms of dementia. The variability in MCI research is influenced by factors such as the source of subjects, the criteria used, and the evaluation methods. Despite these challenges, MCI remains a significant area of study in understanding the progression from normal aging to dementia.Mild cognitive impairment (MCI) is a transitional state between normal aging and early dementia, characterized by cognitive deficits that do not meet the criteria for dementia. It has been proposed as a diagnostic entity to identify individuals at risk of developing Alzheimer's disease (AD). MCI is associated with an increased risk of progression to dementia, particularly AD, and is classified into subtypes based on the cognitive domains affected. The diagnostic criteria for MCI include subjective memory complaints, objective memory impairment, preserved general cognition, normal activities of daily living, and not being demented. The concept of MCI has been refined over time, with various studies highlighting its role in predicting dementia progression. MCI is often distinguished from normal aging and early dementia, though the boundaries can be subtle. Research has shown that MCI can be unstable over time, with some individuals reverting to normal cognitive function. The diagnosis of MCI is challenging due to the lack of strict criteria, but it is considered a clinically useful entity. The application of MCI criteria is similar to those used for dementia and AD, with a focus on cognitive impairment rather than full dementia. The classification of MCI subtypes, such as amnestic MCI (a-MCI) and multiple domain MCI (md-MCI), helps in predicting the likelihood of progression to different forms of dementia. The variability in MCI research is influenced by factors such as the source of subjects, the criteria used, and the evaluation methods. Despite these challenges, MCI remains a significant area of study in understanding the progression from normal aging to dementia.