Words let you down. You think you know what they mean. And then they surprise you by saying something completely different.
I was giving my daughter a lift to school (because her bus, on rainy days, never stops and has to be chased halfway across south London until it lurches to a halt at roadworks or traffic lights), when she said, casually, "I always thought it was, 'I can't be asked.'"
"What?" I said.
"People used to say, aren't you going to do it? And I used to say, no, I can't be asked."
A cyclist wobbles in front of us, helmet flashing in distress.
"Then people used to look at me all offended," says my daughter. "And I used to think, what? What's wrong? And then when I found out what it really was. And I was so embarrassed."
My own teenage years were a fog of misunderstanding. My brother is four years older, and he used to take great delight in giving me bogus definitions of everything from dog tags to taxidermy.
My first proper boyfriend, who was about 13, got me even more muddled. In the first flush of passion he sent me a love letter (those pre-Facebook days) saying he wondered what was installed for us. I was confused for weeks.
"You mustn't worry," I said. "People are always making mistakes. About everything. There was someone on the radio this week who thought Engelbert Humperdinck was in a boy band."
"Who?" she said.
Which just goes to show. You talk and talk and no one understands a word you're saying.