Subtraction

Subtraction adds the additive inverse: $a-b=a+(-b)$. On the number line, $2-3=-1$ is a shift three units left from $2$. Reversing the two inputs changes the sign: $3-2=1$, so subtraction is generally not commutative. Solving $x+3=2$ gives the same answer $x=-1$ by adding $-3$ to both sides; the operation preserves equality while undoing the added amount.

Subtraction is one of the four basic arithmetic operations, alongside addition, multiplication, and division. It involves taking one number away from another. The result of a subtraction operation is called the difference. In a subtraction expression, the number from which another number is taken is called the "minuend," the number that is being subtracted is called the "subtrahend," and the result is known as the "difference.