The best definition of a psychoactive drug is a drug that

A drug that alters brain functions and leads to change in emotions, consciousness and mood of a person.

Explanation: It is a combination of two words; Psycho and Active.

Psycho meaning relating to the wellness of the mind and body.

And Active meaning working or in action.

So, a psychoactive drug is a pharmaceutical product that changes the function of the brain which leads to alterations in behavior and cognition.

They are used for both medical and recreational purposes.

Some of these include; stimulants, antidepressants and anaesthetics.

Psychoactive drugs usually cause brain alterations which the user may find rewarding and which could subsequently lead to addiction.

A drug that alters a person's experiences or consciousness.

Explanation:

A psychoactive medication or psychoactive chemical is a chemical substance that mainly operates on the central nervous system where it affects brain activity. Alcohol and cocaine are examples of psychoactive drugs. It can result to transient perception, mood, consciousness and behavioral changes.

It is a chemical agent that affects brain function and results in vision, mood, awareness, memory, or behavioral alterations.

if an attention line is required on a business letter envelope the united states postal service remmends placing it