She lives next door, and I was bending down to show her an interesting stone.
'Why have you got bald hair, Andrew?' she asked.
'I don't have bald hair. You can't have bald hair.'
'Yes you can. You do...'
'Do you mean a bald head?'
'No! Bald hair!'
'What is bald hair then?'
'It's hair that isn't there!'
And her tone implied that I was being very stupid indeed.
She liked the stone, and carried it off to her collection.