a soft white, grey, or buff limestone composed chiefly of the shells of small marine organisms
a short stick of chalk or chalky material, often coloured, used esp for writing and drawing
as alike/different as chalk and cheese
very different from each other
chalk and talk
Brit, informal traditional teaching methods with use of a blackboard
not by a long chalk
not by any means; not at all
[from the practice of using chalk to mark up points scored in a game]chalky adj
[Old English cealc via West Germanic from Latin calc-, calx lime, from Greek chalix pebble]