Recognizing Zero and One
Be on the lookout for the following special names for zero and one!
Special Properties of $\,0\,$ and $\,1$
 For all real numbers $\,x\,$, $\,x + (x) = 0\,$. A number added to its opposite always gives zero. The opposite of a number is also called the additive inverse.
 For all real numbers $\,x\,$, $\,x\cdot 0 = 0\,$. Any number multiplied by zero gives zero.

For all nonzero real numbers $\,x\,$, $\,\displaystyle\frac{x}{x} = x\cdot\frac{1}{x} = 1\,$. A nonzero number divided by itself (or multiplied by its reciprocal) always gives one.
The number $\,\frac{1}{x}\,$ is called the reciprocal of $\,x\,$ or the multiplicative inverse of $\,x\,$. Multiplying a number by its reciprocal gives the number $\,1\,$. Every nonzero number has a reciprocal; zero does not have a reciprocal.
Examples
Decide if the given number is $\,0\,$, $\,1\,$, or a different number:
$\displaystyle\frac13 + (\frac 13)$  Answer: $\,0\,$ 
$\displaystyle 0\cdot\frac 13$  Answer: $\,0\,$ 
$\displaystyle 2\cdot \frac{1}2$  Answer: $\,1\,$ 
$\displaystyle\frac{1/7}{1/7}$  Answer: $\,1\,$ 
$\displaystyle 3\bigl(\frac13\bigr)$  Answer: not $\,0\,$, and not $\,1$ 