Some semanticists, therefore, object to designating them as drugs. Non-medical use of drugs has been avoided here purposely since it conveys the tacit implication that medical usage is free from dependence and abuse. It identifies drug abuse specifically with self-administration. Many terms have been utilized to characterize what is currently termed drug dependence by an increasing majority of the scientific and legal communities. The most commonly used terms prior to 1965 were habituation and addiction. Habituation usually characterized drug use without serious harmful effects to the individual and especially to society. Determination of the existence of psychological dependence on drugs therefore requires an arbitrary decision relating to the frequency and duration of reinforcements. This is difficult to accomplish since the strength of the reinforcement is critical, a factor that varies not only with the chemical, physical, and pharmacological characteristics of the drug, but also with the dose, method, frequency, and duration of administration.