The National Coalition for Sexual Freedom glossary defines sadism as deriving gratification or pleasure from inflicting physical or emotional pain. That can mean impact, pressure, biting, scratching, humiliation, fear, strain, or the anticipation of an ordeal. The difficult quality of the experience is part of the appeal.

What attracts the sadist can be just as specific as the activity. It may be the physical act, careful control of a build, a visible reaction, the receiver's endurance, or the tone between them. In interviews with 33 people in 17 long-term BDSM relationships, one dominant described the partner's excitement as the source of his own enjoyment: spanking appealed when the other person was excited by being spanked.

Someone may enjoy giving heavy thud but dislike sharp sting, or like causing embarrassment but have no interest in physical pain. A narrow interest does not require sadist as an identity.

The same NCSF glossary places masochism on the receiving side of physical or emotional pain. Pleasure may lie in the immediate sensation, a slow build, meeting a challenge, the emotional meaning, or the release afterwards. Receiving an ordeal does not automatically mean enjoying every part of it in isolation.

Masochistic preferences are often narrow. Sting, thud, pressure, muscle effort, helplessness, humiliation, and fear are different experiences. A person might enjoy an escalating thud, dislike sudden sting, want no marks, and find humiliation unappealing.

A person can enjoy a difficult sensation without wanting to submit. They may choose the activity, specify the pace, direct the giver, or treat receiving as a display of strength.

A sadist and a masochist can enjoy the same event from opposite directions. That makes them an obvious pairing, but not an automatic match. One may want sharp sting while the other wants heavy thud. One may enjoy visible reactions while the other becomes quiet and inward. Marks, pace, tone, anticipation, and endurance can matter differently to each person.

The relationship interviews make that separation concrete. All 15 non-switch dominant and submissive couples matched on their power roles, but five did not match on sadist and masochist identification. Two paired a sadistic dominant with a specifically non-masochistic submissive, while three paired a masochistic submissive with a specifically non-sadistic dominant. This was a small Arizona community sample interviewed in 2001 and 2002, not a population estimate.

Someone who likes both directions may use sadomasochist, use both labels, or describe the activities instead. If they say they switch, it helps to ask whether they mean power, action, or the direction of S/M interest.

The NCSF glossary's separate definitions place dominance and submission on control, sadism and masochism on giving and receiving pain, and top and bottom on the doer and receiver in an activity. It also states that a D/s dynamic need not contain S/M. These axes often line up, but they answer different questions.

In the same study of 17 relationships, six of the 15 dominants also identified as masochistic. Some directed a submissive to apply stimulation to them, and respondents located the power exchange in who chose the stimulation, not who received it. A dominant masochist can therefore bottom for an activity without giving up authority. A submissive sadist can top by applying the sensation under that dominant's direction.

Topping does not by itself make someone a sadist. They may enjoy technique, service, performance, or the receiver's pleasure without enjoying the ordeal. Bottoming does not by itself make someone a masochist either. A person may receive rope, impact, or another activity for its role, ritual, or closeness.

The words began as medical categories, not as neutral labels created by the modern BDSM community. Historian Harry Oosterhuis records that Richard von Krafft-Ebing introduced sadism and masochism around 1890 in later editions of Psychopathia Sexualis and in Neue Forschungen auf dem Gebiet der Psychopathia sexualis. He drew sadism from the Marquis de Sade and masochism from Austrian writer Leopold von Sacher-Masoch.

That history helps explain why the words still carry meanings outside kink. Sadistic can be an accusation of cruelty, while masochistic can describe apparently self-defeating behaviour. Those uses do not define a person's BDSM interests.

Clinical manuals also contain sexual sadism disorder and sexual masochism disorder. The American Psychiatric Association's DSM-5 explanation says most people with atypical sexual interests do not have a mental disorder and distinguishes an interest from a disorder through personal distress beyond social disapproval or criteria involving harm to others. The Sadist Test and Masochist Test compare scene interests and motives; they are not clinical assessments.

The Sadist Test compares motives for giving an ordeal. The Masochist Test compares motives for receiving one. The Impact Play Quiz compares tools, rhythm, and sensation; the Spanking Test focuses on spanking; the Pain Play Quiz compares intensity, duration, sensation variety, and emotional meaning.

A systematic review of 87 BDSM research articles found that studies using an umbrella label such as S/M or BDSM tended to produce lower estimates than studies asking about named activities. The finding concerns survey wording, but it shows why a broad label cannot substitute for details.

When describing your own interest, name the activity, sensation, direction, power role, and tone that matter. 'I like giving heavy thud in a playful scene between equals' says more than sadist alone.