What it means
Used when two people or things are completely different, even if they look like they ought to go together or came from the same place. It’s a very British way of saying the gap between them is massive, not just a tiny clash in taste.
Usage examples
"They’re sisters but chalk and cheese: one’s dead posh and obsessed with spreadsheets, the other’s a skint artist living in a van."
"The two brothers are chalk and cheese, one is a quiet bookworm and the other never stops talking."
"People expect the sequel to feel the same, but it is chalk and cheese compared to the original."
"Me and my cousin grew up in the same house, but we're chalk and cheese. He’s up at six doing triathlons and I’m arguing with the kettle."
"On paper those two flats look similar, but in real life they’re chalk and cheese."
Where it comes from
This one’s old in British English and is recorded from the 19th century. The point is the contrast. Chalk and cheese can both appear pale and solid at a quick glance, but they’re totally unlike each other in substance, taste, and use. That made the pairing a neat way to say two things don’t match at all.
This expression also appears in
