Health
Pratchett is to donate $1m for research into Alzheimer's disease.
He was diagnosed with a rare early-onset form of the disease.
Terry Pratchett, 59, announced the pledge of about £494,000 at the Alzheimer's Research Trust annual conference.
Personally, I'd eat the arse out of a dead mole if it offered a fighting chance
There are 15,000 people in the UK with early-onset dementia, which strikes under the age of 65 years.
Mr Pratchett has a rare form of the disease called posterior cortical atrophy, in which areas at the back of the brain begin to shrink and shrivel.
He says he is starting to notice its effect on him.