The combining form milli- denotes which fraction?

• A. 1/100th
• B. 1/10th
• C. 1/1000th
• D. 1/10000th

Answer: (C)

Milli- indicates one thousandth of the base unit. In medical terms, that means a millimeter is one thousandth of a meter and a milligram is one thousandth of a gram. So the fraction described by milli- is 1/1000. The other fractions correspond to different prefixes (centi- for 1/100, deci- for 1/10), while 1/10,000 isn’t a common prefix used in standard medical terminology.