gaiety
词根词缀：
anxiety n. 焦虑
anxious 担忧的 + ety 性质，状态 → 焦虑
dubiety n. 怀疑
dubious 怀疑的 + ety 性质，状态 → 怀疑
gaiety n. 快乐
gay 快乐的 + ety 性质，状态 → 快乐
naivety n. 天真
naive 天真的 + ety 性质，状态 → 天真
propriety n. 适合，得体
proper 适合的 + ety 性质，状态 → 适合，得体
satiety n. 饱足，厌腻
sati 足够，饱足 + ety 性质，状态 → 饱足，厌腻
sobriety n. 头脑清醒
sober 头脑清醒的 + ety 性质，状态 → 头脑清醒
subtlety n. 微妙；狡猾
subtle 微妙的；狡猾的 + ety 性质，状态 → 微妙；狡猾
variety n. 变化，多样化
vari 变化 + ety 性质，状态 → 变化，多样化
数据来源：新东方英语词汇速记大全
相关例句：
The gaiety with which they had set out had somehow vanished; and yet there was no enmity or malice between them.
她们一块儿出门时的欢乐情绪也不知道怎么消失了；但是在她们中间并没有仇恨和恶意。
She brought him a sense of fun, of gaiety that filled a gap in his life.
她带给他开心快乐，弥补了他生命中的缺憾。
They laughed and were gay, not in the least because there was reason for laughter. But they were gay and glad at heart, and so everything that happened was reason enough for gaiety and laughter in them.
他们高兴地笑闹，不是因为有值得笑的理由；但他们心里感到高兴和愉快，所以，无论发生什么事，都是他们开心和笑的理由。
Color flags added to the gaiety of the festival.
彩旗增加了节日的欢乐。
Too much gaiety or laughter would jar upon their almost sacred quiet.
过多的欢乐和嬉笑都会干扰她们那几乎神圣肃穆的宁静。
Paris is a city of gaiety and pleasure where four fifths of the inhabitant die of grief.
巴黎，是个有五分之四的居民死于悲伤的快乐城。