A stop word is a predetermined word that the bottom can say to stop the action. When the stop word is spoken, all thematic actions stop, and if the bottom is in bondage, he is released from it. The need for such a word comes directly from one of the three basic ethical principles of BDSM: voluntariness. This principle involves not only consenting to the initiation of the action, but also maintaining voluntariness throughout the thematic actions. In other words, the bottom retains the right to interrupt the action at any time. And since during the practices cries of pain do not mean a bent to stop, and ordinary words (e.g. "no", "enough") can be part of role-playing, or a consequence of ambivalence of emotions, and do not mean a real desire to interrupt the action - a special word for stopping is required. A stop word is also necessary for safety - the Upper is not telepathic, and may not notice many dangerous situations: a pinched nerve, heart attack, .spasm, etc. In this case, the stop word allows the lower to stop the action if the situation has become critical, and it is not obvious to the Upper. It is important to note that the presence of such a word does not remove the Upper's responsibility for the safety of the action. Often the lower cannot assess the danger on his own, or is not able to adequately perceive what is happening (e.g. in a state of euphoria during sub-space). Many inferiors, for various reasons, do not want to utter a stop word even in a critical situation. It is also possible that prolonged painful exposures cause a decrease in sensitivity to pain (this state is called a "wall"). Therefore, the Upper always monitors the condition of the Lower on his own, not relying only on the stop word. There are various variations of stop words. The main requirement is the impossibility of accidental pronunciation of such a word, it must immediately stand out from the context of the action, attracting attention. In particular, in English-speaking BDSM the word "Anteater" is traditionally used. A good option is the "traffic light" system. Red - means immediate cessation of action, yellow - signals about approaching the threshold of influence, green - signals the possibility to continue (usually in response to the Upper's question "Color?"). It is necessary to say that not always the bottom has the opportunity to say something - for example, he may have a gag in his mouth. Therefore, the signal to stop the influence can be an action - a sequence of gestures. An object clasped in the hand, which the lower person drops not only at will, but also in case of loss of consciousness, works well. In practice, there are cases when in permanent couples who have been holding sessions for a long time, the lower one declares refusal of the stop word, it is "given", and so on. It should be understood that in reality this does not mean that it is impossible to interrupt the action in case of an emergency - it only means that the pair has developed a system of state estimation and a system of signals about it, which differs from the previously accepted one. The upper one's demand for the initial refusal of the stop word and rejection of it is a sign of inadequacy and a signal that it is impossible to consider it as a partner.