millionth

One millionth is equal to 0.000 001, or 1 x 10⁻⁶ in scientific notation. It is the reciprocal of a million, and can be also written as {{frac|1|1,000,000}}.{{citation|title=Science and Sensibility: The Elegant Logic of the Universe|first=Keith J.|last=Laidler|date=30 December 2011 |publisher=Prometheus Books|isbn=9781615927036|page=15|url=https://books.google.com/books?id=Z_qP62qOhvYC&pg=PA15}}. Units using this fraction can be indicated using the prefix "micro-" from Greek, meaning "small".{{citation|title=The American Heritage Guide to Contemporary Usage and Style|publisher=Houghton Mifflin Company|year=2005|isbn=9780618604999|page=300|url=https://books.google.com/books?id=xb6ie6PqYhwC&pg=PA300}}. Numbers of this quantity are expressed in terms of μ (the Greek letter mu).{{citation|title=Principles of Engineering|first1=Brett|last1=Handley|first2=Craig|last2=Coon|first3=David|last3=Marshall|publisher=Cengage Learning|year=2011|isbn=9781435428362|page=212|url=https://books.google.com/books?id=3YBeXkp-AacC&pg=PT212}}.

"Millionth" can also mean the ordinal number that comes after the nine hundred, ninety-nine thousand, nine hundred, ninety-ninth and before the million and first.{{citation|title=Grammar: A Student's Guide|first=James R.|last=Hurford|authorlink=James Hurford|publisher=Cambridge University Press|year=1994|isbn=9780521456272|page=146|url=https://books.google.com/books?id=ZaBKd8pT6kgC&pg=PA146}}.