# What part of a liter is one milliliter?

$\text{One thousandth}$
The prefix $\text{milli } \equiv 1 \times {10}^{-} 3$
Thus $1 \cdot L \equiv {10}^{3} \cdot m L$ $=$ $\cancel{{10}^{3} \cdot m L} \times \cancel{{10}^{-} 3} \cdot L \cdot \cancel{m {L}^{-} 1}$ $=$ $1 \cdot L$ as required.