These words are related in that they all mean to restore to a state of peace, quiet or order. Quell , suppress and subdue mean to put an end to a disturbance, such as a riot or a revolt, by the use of persuasion or force. To quell an uprising, one may employ either persuasion or force, or both; and the word suggests taking measures to discourage the participants in order to keep the situation from getting out of hand: The sergeants were able to quell the mêlée that broke out in the barracks by ordering all the men to stand to attention. Used figuratively, quell may mean merely to allay or quiet, as in the case of certain feelings: to quell foolish fears; the mother’s happiness in the event often quelling the pains attending childbirth. Suppress in this sense means to quell by taking specific actions that will not only put down a disturbance completely but will frustrate any attempts to revive it or to start a similar one. The word suggests a complete crushing and overpowering, often swift and violent in nature: to suppress a mutiny by putting half the crew in irons and hanging the ringleaders at dawn. Subdue takes the participants in a disturbance as its object and implies that they are not only reduced to order but, by the imposition of controls (such as curfews or threats of reprisal), are also rendered more or less incapable of resisting further. In addition to the implication of conquering completely, subdue also carries the idea of taming or rendering mild and gentle, often after greater difficulty: The great, thundering stallion was finally subdued and broken in as a riding horse.

Calm and placate are milder in meaning than the foregoing words and apply only to the quietening of violent movement or emotion. Calm is the more general term here and implies causing a state of quietude – which may be only transient.

• The nurses calmed the anxious patient with soothing words and small attentions; While awaiting trial, the angry prisoner calmed down enough to co-operate with his lawyer in preparing his defence.

Placate always involves appeasement and means to calm anger, resentment, hostility, etc., by making concessions or yielding to demands: Only by offering to do extra work at the end of the term could be placate the teacher who seemed determined to fail him.

Tranquillize , still a fad word after some years of use, is a back-formation from the medical term tranquillizer , which is applied to a class of drugs having the property of reducing nervous tension and states of anxiety. It is rarely used in the sense of calm or pacify and almost always refers to the effect produced by these drugs.