plural dementias
medical
: a mental illness that causes someone to be unable to think clearly or to understand what is real and what is not real
This patient suffers from dementia.
a new study on age-related dementias
Cite this Entry
“Dementia.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/dementia. Accessed 18 Jun. 2026.
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