Suzanne Catty, author of Hydrosols: The Next Aromatherapy proposes the following definition:

 

"Hydrosols are the condensate water co-produced during the steam- or hydro-distillation of plant material for aromatherapeutic purposes."

​

[Suzanne Catty, Hydrosols: The Next Aromatherapy (Rochester, VT: Healing Arts Press, 2001), 10.]