Which term describes a state of relaxation or peace of mind?

The term "repose" specifically refers to a state of rest, tranquility, or peace of mind. It conveys a sense of calmness and relaxation, indicating a mental or physical state where one is free from disturbance or agitation. This definition aligns closely with the question, as it directly addresses the idea of relaxation and peace of mind.

On the other hand, "soporific" relates to inducing sleep or causing drowsiness, which while related to relaxation, does not capture the broader sense of peace of mind. "Quiescent" refers to a state of inactivity or dormancy, which can suggest stillness but lacks the connotation of mental serenity. "Virulent" typically describes something harmful or hostile, particularly in relation to diseases, and thus does not relate at all to concepts of relaxation or peace.