愉快

 Though I knew all these colocations well before it never occurred to me there are a lot of ways to describe happy in Chinese and perhaps more, certainly by frequency, than in English
开心 – open hearted i.e. well disposed in other words happy, inner attitude
高兴 – gāoxìng excited and happy, external stimulus
快乐 – kuaile used for expressing wishes
愉快 – yúkuài joyous, relaxed, pleasant
幸福 – xìngfú happiness in ones life