joyful,pleasant和happy的区别?

joyful,pleasant和happy的区别?
请不要复制词典的内容!最好给出一些例子来,

意思都含“快乐的”、“高兴的”.
happy 是常用词,本义是“幸福的”,指“由于幸福、满足而感到快乐”,如:
He was very happy to hear that .
听到那,他很快乐.
joyful指“一种外来事件使情绪强烈、起劲、愉快的”,如:
They were singing and dancing to celebrate this joyful occasion.
他们唱着、跳着庆祝这令人欢乐的时刻.
pleasant 是常用词,指“愉快的”,强调“所形容的人或物有给予愉快的性质”,如:
We spent a very pleasant evening.
我们度过了一个愉快的夜晚.
----Will