##  [Water Activity (Aw)](/water-activity-aw) 

  ##  [Water Activity (Aw)](https://health.quantumdictionary.io/water-activity-aw-0) 

  

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**Health & Life Sciences Dictionary**

 







 

 

 

 



 

 

 

 

Definition

The dimensionless ratio of the vapor pressure of water in a food sample to the vapor pressure of pure water at the same temperature (range 0–1), representing the fraction of water that is thermodynamically available to participate in microbial growth, chemical reactions and physical processes; distinct from total moisture content because solutes and binding reduce availability without changing tot