factor IX


: a clotting factor that activates factor VIII and whose deficiency is associated with hemophilia

called also Christmas factor

Examples of factor IX in a Sentence

Recent Examples on the Web The standard care for severe hemophilia B is lifelong intravenous infusions of factor IX concentrate, sometimes weekly or even more frequently. Jacqueline Howard, CNN, 22 July 2022 For example, factor IX clotting factor is not harmful at high levels, and people with haemophilia B already inject themselves with huge amounts of it. Ed Yong, Discover Magazine, 25 Apr. 2012

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'factor IX.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1955, in the meaning defined above

Time Traveler
The first known use of factor IX was in 1955

Dictionary Entries Near factor IX

Cite this Entry

“Factor IX.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/factor%20IX. Accessed 23 May. 2024.

Medical Definition

factor IX

: a clotting factor that activates factor VIII and whose absence is associated with hemophilia B

called also autoprothrombin II, Christmas factor

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