Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory deficits and cognitive decline. The primary pathological features, amyloid plaques and neurofibrillary tangles, have been recognized for over a century and remain essential for diagnosis. AD is the most common cause of dementia globally, with no effective treatments available except in a few familial cases driven by genetic mutations. The disease is often associated with other age-related processes such as cerebrovascular disease and Lewy body disease, complicating diagnostic and therapeutic efforts. This review outlines the etiologically linked pathologic features of AD, including amyloid plaques, neurofibrillary tangles, granulovacuolar degeneration, and Hirano bodies, as well as other co-pathologies like cerebrovascular disease and Lewy body disease. The review also discusses the clinical heterogeneity of AD, including atypical presentations and subtypes, and the neuropathological criteria for diagnosis. The relationship between various co-pathologies and their impact on diagnosis and treatment is an active area of research.Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory deficits and cognitive decline. The primary pathological features, amyloid plaques and neurofibrillary tangles, have been recognized for over a century and remain essential for diagnosis. AD is the most common cause of dementia globally, with no effective treatments available except in a few familial cases driven by genetic mutations. The disease is often associated with other age-related processes such as cerebrovascular disease and Lewy body disease, complicating diagnostic and therapeutic efforts. This review outlines the etiologically linked pathologic features of AD, including amyloid plaques, neurofibrillary tangles, granulovacuolar degeneration, and Hirano bodies, as well as other co-pathologies like cerebrovascular disease and Lewy body disease. The review also discusses the clinical heterogeneity of AD, including atypical presentations and subtypes, and the neuropathological criteria for diagnosis. The relationship between various co-pathologies and their impact on diagnosis and treatment is an active area of research.