the effective concentration of a substance.
How Do You Change Passive Voice Into Active Voice?In active voice, the subject performs the action of the verb. In passive voice, the subject receives the action of the verb. If you feel like you need a little more than that, keep reading.
Origin of active mass
First recorded in 1905–10
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019