An estimated 5.5 million Americans of all ages have Alzheimer's disease. Of the estimated 5.5 million Americans living with Alzheimer's dementia in 2017, an estimated 5.3 million are age 65 and older and approximately 200,000 individuals are under age 65 and have younger-onset Alzheimer's. One in 10 people age 65 and older (10 percent) has Alzheimer's dementia.
Major dictionaries. The longest word in any of the major English language dictionaries is pneumonoultramicroscopicsilicovolcanoconiosis, a word that refers to a lung disease contracted from the inhalation of very fine silica particles, specifically from a volcano; medically, it is the same as silicosis.
So what if we want a word that is not famous for being long, but a word that describes something real. What's the longest one of those? Science writer Sam Kean, in his book The Disappearing Spoon, worked really hard on this and after much sleuthing, he landed on a word that comes not from dancing English nannies but from virus-hunting scientists.