A Mathematical and Philosphical Dictionary
, in Algebra, is the reducing a compound equation, or quantity, to a more simple form of expression. This is done either to save room, or the trouble of writing a number of symbols; or to simplisy the expression, either to ease the memory, or to render the formula more easy and general.
So the equation , by putting p = a, q = ab, and r = abc, becomes
And the equation , by putting , and , becomes .