1. In electroencephalography, the presence of neurogenic electrical energy.

2. In physical chemistry, an ideal concentration for which the law of mass action will apply perfectly; the ratio of the activity to the true concentration is 3. For enzymes, the amount of substrate consumed (or product formed) in a given time under given conditions; turnover number.

blocking activity

insulin-like activity

intrinsic sympathomimetic activity

nonsuppressible insulin-like activity

optical activity

plasma renin activity

specific activity

triggered activity