(medicine) The lowest pharmaceutical dosage required to cause effect in 50% of average individuals.

(physics) The increase in the wavelength, and corresponding decrease in the energy, of photons (especially of X-rays and gamma rays) when scattered by interaction with matter

(quantum field theory) The effect of the Casimir force.

The state in which a series of repeated actions have an effect greater than the sum of their individual effects; noted especially in the repeated administration of drugs or repeated consumption of trace elements or chemicals that show no immediate effect.

plural of sound effect

To become enforceable, or applicable.

An accelerating growth of magnitude, including fame, fortune, importance, or danger.

The circumstance in which one event instigates an expansive set of other events.

(aeronautics) Any aerodynamic effects occurring due to a vehicle's body or appendages moving in close proximity to the ground.

(sciences) A side-effect, especially a negative one in pharmacology.