Calculus
<B>1.</B> A stone within the body, such as a stone in the urinary tract.
<B>2.</B> The calcium salt deposits on the teeth.
<B>3.</B> A field of mathematics.
These different meanings of 'calculus' all go bach to the origin of the word.
In Latin, a calculus is 'a pebble.' Pebbles were once used for counting, from which came the mathematical field of calculus.
A urinary calculus is a literally pebble in the urinary system.
And the calculus on the teeth is, like a urinary stone, an abnormal concretion of mineral salts within the body