Also found in: Acronyms.
An initialism of "Parentheses, Exponents, Multiplication and Division, Addition and Subtraction," used as a mnemonic in mathematics for remembering the order of operations when calculating an expression. If you find yourself getting confused about whether to square the value before you divide while solving for X and Y, just remember what PEMDAS stands for! A: "I know the answer! X equals 75!" B: "You forgot about PEMDAS—you didn't multiply the two values before subtracting them from the third."
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.