quietude(n = noun.feeling) quietness, tranquility, tranquillity - a state of peace and quiet;
is a kind of calmness
has particulars: ataraxis, heartsease, peace, peace of mind, peacefulness, repose, serenity, easiness, relaxation

   Rest; repose; quiet; tranquillity. Shelley. [1913 Webster]

quietude, n. a state of quiet.

N  inexcitability, imperturbability, inirritability, even temper, tranquil mind, dispassion, tolerance, patience, coolth, passiveness, hebetude, hebetation, impassibility, stupefaction, coolness, calmness, composure, placidity, indisturbance, imperturbation, sang froid, tranquility, serenity, quiet, quietude, peace of mind, mental calmness, staidness, gravity, sobriety, Quakerism, philosophy, equanimity, stoicism, command of temper, self-possession, self-control, self-command, self-restraint, ice water in one's veins, presence of mind, submission, resignation, sufferance, supportance, endurance, longsufferance, forbearance, longanimity, fortitude, patience of Job, patience on a monument, patience 'sovereign o'er transmuted ill', moderation, repression of feelings, subjugation of feeling, restraint, tranquillization, inexcitable, unexcitable, imperturbable, unsusceptible, unpassionate, dispassionate, cold-blooded, irritable, enduring, stoical, Platonic, philosophic, staid, stayed, sober, sober minded, grave, sober as a judge, grave as a judge, sedate, demure, cool-headed, easy-going, peaceful, placid, calm, quiet as a mouse, tranquil, serene, cool as a cucumber, cool as a custard, undemonstrative, temperate, composed, collected, unexcited, unstirred, unruffled, undisturbed, unperturbed, unimpassioned, unoffended, unresisting, meek, tolerant, patient, patient as Job, submissive, tame, content, resigned, chastened, subdued, lamblike, gentle as a lamb, suaviter in modo, mild as mothers milk, soft as peppermint, armed with patience, bearing with, clement, long-suffering, like patience on a monument smiling at grief, aequo animo, in cold blood, more in sorrow than in anger, Int, patience!, and shuffle the cards, cool calm and collected, keep calm in the midst of a storm, adversity's sweet milk, philosophy, mens aequa in arduis philosophia stemma non inspec, quo me cumque rapit tempestas deferor hospes, they also serve who only stand and wait.