The concept of mild cognitive impairment (MCI) has emerged as an intermediate state between normal aging and early dementia. MCI is characterized by subtle cognitive decline that does not meet the criteria for dementia but is associated with an increased risk of developing dementia over time. The diagnosis of MCI involves clinical criteria that include subjective memory complaints, objective memory impairment for age, relatively preserved general cognitive function, intact functional activities, and not meeting the criteria for dementia. Various subtypes of MCI have been identified, including amnestic MCI (a-MCI) and non-amnestic MCI (na-MCI), which can further be classified based on the presence or absence of multiple cognitive domains affected. The diagnosis of MCI is similar to the diagnosis of dementia or Alzheimer's disease (AD), with the key difference being the threshold for cognitive impairment. The article discusses the challenges in defining normal aging and the variability in the literature due to different criteria and sources of subjects. It emphasizes the importance of clinical judgment in diagnosing MCI and highlights the need for further research to refine diagnostic criteria and develop targeted therapeutic interventions for specific subtypes of MCI.The concept of mild cognitive impairment (MCI) has emerged as an intermediate state between normal aging and early dementia. MCI is characterized by subtle cognitive decline that does not meet the criteria for dementia but is associated with an increased risk of developing dementia over time. The diagnosis of MCI involves clinical criteria that include subjective memory complaints, objective memory impairment for age, relatively preserved general cognitive function, intact functional activities, and not meeting the criteria for dementia. Various subtypes of MCI have been identified, including amnestic MCI (a-MCI) and non-amnestic MCI (na-MCI), which can further be classified based on the presence or absence of multiple cognitive domains affected. The diagnosis of MCI is similar to the diagnosis of dementia or Alzheimer's disease (AD), with the key difference being the threshold for cognitive impairment. The article discusses the challenges in defining normal aging and the variability in the literature due to different criteria and sources of subjects. It emphasizes the importance of clinical judgment in diagnosing MCI and highlights the need for further research to refine diagnostic criteria and develop targeted therapeutic interventions for specific subtypes of MCI.