1)pleased指外物作用于感官,使人感到"高兴 、满意、喜欢",常见的结构为:be pleased+不定式或从句,be pleased with,be pleased at (about)。例如:

I'm very pleased with the performance.

We're pleased about (at) your success.

I'm quite pleased that she has got such a good chance.

2)pleasant意为"令人愉快的,舒畅的,非常好的,讨人喜欢的,风趣的"。例如:

they spent a very pleasant afternoon in the hills.

Spring weather is pleasant.

He talked in a pleasant way.

3)pleasing指某物或某人"使他人高兴、招人喜爱"。例如:

these flowers are very pleasing.

the girl has pleasing manners.

4)pleasure是名词,指"快乐,愉快的事,乐趣"。例如:It's a pleasure to meet you.

May I have the pleasure of dancing with you.