There are over a thousand different psychotherapy techniques, some being minor variations, while others are based on very different conceptions of psychology, ethics (how to live) or techniques. Most involve one-to-one sessions, between client and therapist, but some are conducted with groups, including families. Psychotherapists may be mental health professionals such as psychiatrists, psychologists, clinical social workers, marriage and family therapists, or professional counselors. Psychotherapists may also come from a variety of other backgrounds, and depending on the jurisdiction may be legally regulated, voluntarily regulated or unregulated (and the term itself may be protected or not).
The term psychotherapy is derived from Ancient Greek psyche (ψυχή meaning "breath; spirit; soul") and therapeia (θεραπεία "healing; medical treatment"). The Oxford English Dictionary defines it now as "The treatment of disorders of the mind or personality by psychological methods..."
The American Psychological Association adopted a resolution on the effectiveness of psychotherapy in 2012 based on a definition developed by John C. Norcross: "Psychotherapy is the informed and intentional application of clinical methods and interpersonal stances derived from established psychological principles for the purpose of assisting people to modify their behaviors, cognitions, emotions, and/or other personal characteristics in directions that the participants deem desirable". Influential editions of a work by psychiatrist Jerome Frank defined psychotherapy as a healing relationship using socially authorized methods in a series of contacts primarily involving words, acts and rituals—regarded as forms of persuasion and rhetoric.
Some definitions of counseling overlap with psychotherapy (particularly in non-directive client-centered approaches), or counseling may refer to guidance for everyday problems in specific areas, typically for shorter durations with a less medical or 'professional' focus. Somatotherapy refers to the use of physical changes as injuries and illnesses, and sociotherapy to the use of a person's social environment to effect therapeutic change. Psychotherapy may address spirituality as a significant part of someone's mental / psychological life, and some forms are derived from spiritual philosophies, but practices based on treating the spiritual as a separate dimension are not necessarily considered as traditional or 'legitimate' forms of psychotherapy.
Historically, psychotherapy has sometimes meant "interpretative" (i.e. Freudian) methods, namely psychoanalysis, in contrast with other methods to treat psychiatric disorders such as behavior modification.