1.  cheerfulness(n = noun.attribute) cheer, sunniness, sunshine - the quality of being cheerful and dispelling gloom; "flowers added a note of cheerfulness to the drab room"
is a kind of attribute
is a part of disposition, temperament
has particulars: good-humoredness, good-humouredness, good-naturedness, good-temperedness
Antonym: uncheerfulness
Derived form adjective cheerful₁

2.  cheerfulness(n = noun.feeling) blitheness - a feeling of spontaneous good spirits; "his cheerfulness made everyone feel better"
is a kind of happiness
has particulars: buoyancy, perkiness, carefreeness, insouciance, lightheartedness, lightsomeness
Antonym: cheerlessness
Derived form adjective cheerful₂

   Good spirits; a state of moderate joy or gayety; alacrity. [1913 Webster]

N  pleasure, gratification, enjoyment, fruition, oblectation, delectation, delection, relish, zest, gusto, satisfaction, complacency, well-being, good, snugness, comfort, ease, cushion, sans souci, without worry, mind at ease, joy, gladness, delight, glee, cheer, sunshine, cheerfulness, treat, refreshment, amusement, luxury, mens sana in corpore sano, a sound mind in a sound body, happiness, felicity, bliss, beatitude, beautification, enchantment, transport, rapture, ravishment, ecstasy, summum bonum, paradise, elysium, third heaven, seventh heaven, cloud nine, unalloyed happiness, hedonics, hedonism, honeymoon, palmy days, halcyon days, golden age, golden time, Dixie, Dixie's land, Saturnia regna, Arcadia, Shangri-La, happy valley, Agapemone, pleased, not sorry, glad, gladsome, pleased as Punch, happy, blest, blessed, blissful, beatified, happy as a clam at high water, happy as a clam, happy as a king, happy as the day is long, thrice happy, ter quaterque beatus, enjoying, joyful, hedonic, in a blissful state, in paradise, in raptures, in ecstasies, in a transport of delight, comfortable, at ease, content, sans souci, overjoyed, entranced, enchanted, enraptures, enravished, transported, fascinated, captivated, with a joyful face, with sparkling eyes, pleasing, ecstatic, beatic, painless, unalloyed, without alloy, cloudless, happily, with pleasure, with glee, one's heart leaping with joy, a wilderness of sweets, I wish you all the joy that you can wish, jour de ma vie, joy ruled the day and love the night, joys season'd high and tasting strong of guilt, oh happiness, our being's end and aim!, there is a pleasure that is born of pain, throned on highest bliss, vedi Napoli e poi muori, zwischen Freud und Leid ist die Brucke nicht weit, the bridge between joy and sorrow is not wide.

N  content, contentment, contentedness, complacency, satisfaction, entire satisfaction, ease, heart's ease, peace of mind, serenity, cheerfulness, ray of comfort, comfort reconciliation, resignation, waiter on Providence, content, contented, satisfied, at ease, at one's ease, at home, with the mind at ease, sans souci, sine cura, easygoing, not particular, conciliatory, unrepining, of good comfort, resigned, cheerful, unafflicted, unvexed, unmolested, unplagued, serene, at rest, snug, comfortable, in one's element, satisfactory, tolerable, good enough, OK, all right, acceptable, contently, contentedly, to one's heart's content, a la bonne heure, all for the best, Int, amen, very well, all the better, so much the better, well and good, it will do, that will do, it cannot be helped, nothing comes amiss, a heart with room for every joy, ich habe genossen das irdische Gluck ich habe gele, nor cast one longing lingering look behind, shut up in measureless content, sweet are the thoughts that savor of content, their wants but few their wishes all confined, might as well relax and enjoy it.

N  cheerfulness, geniality, gayety, l'allegro, cheer, good humor, spirits, high spirits, animal spirits, flow of spirits, glee, high glee, light heart, sunshine of the mind, sunshine of the breast, gaiete de coeur, bon naturel, liveliness, life, alacrity, vivacity, animation, allegresse, jocundity, joviality, jollity, levity, jocularity, mirth, merriment, hilarity, exhilaration, laughter, merrymaking, heyday, rejoicing, marriage bell, nepenthe, Euphrosyne, sweet forgetfulness, optimism, self complacency, hedonics, hedonism, cheerful, happy, cheery, cheerly, of good cheer, smiling, blithe, in spirits, in good spirits, breezy, bully, chipper, in high spirits, in high feather, happy as the day is long, happy as a king, gay as a lark, allegro, debonair, light, lightsome, light hearted, buoyant, debonnaire, bright, free and easy, airy, janty, jaunty, canty, hedonic, riant, sprightly, sprightful, spry, spirited, spiritful, lively, animated, vivacious, brisk as a bee, sparkling, sportive, full of play, full of spirit, all alive, sunny, palmy, hopeful, merry as a cricket, merry as a grig, merry as a marriage bell, joyful, joyous, jocund, jovial, jolly as a thrush, jolly as a sandboy, blithesome, gleeful, gleesome, hilarious, rattling, winsome, bonny, hearty, buxom, playful, playsome, folatre, playful as a kitten, tricksy, frisky, frolicsome, gamesome, jocose, jocular, waggish, mirth loving, laughter-loving, mirthful, rollicking, elate, elated, exulting, jubilant, flushed, rejoicing, cock-a-hoop, cheering, inspiriting, exhilarating, cardiac, cardiacal, pleasing, palmy, cheerfully, Int, never say die!, come!, cheer up!, hurrah!, hence loathed melancholy!, begone dull care!, away with melancholy!, a merry heart goes all the day, as merry as the day is long, ride si sapis.