1 easy to see, hear or understand; clear 清晰的；清楚的；明白的；浅易的: It was plain that he didn't want to talk about it. 他显然不想谈论这件事。She made it plain that she didn't want to see me again. 她明确表示她不想再见到我。

2 (used about people, thoughts, actions, etc) saying what you think; direct and honest （指人、思想、行动等）直截了当的，坦率的，真诚的: I'll be plain with you. I don't like the idea. 坦白对你说，我不喜欢那主意。

3 simple in style; not decorated or complicated 朴素的；简朴的；简单的: My father likes plain English cooking. 我父亲喜欢清淡的英国菜。

4 (only before a noun 只用于名词前) all one colour; without a pattern on it 单色的；没有花纹的；素净的: a plain blue jumper 素净的蓝色套头毛衣

5 (used especially about a woman or girl) not beautiful or attractive （尤指妇女或女孩）不美的，相貌平庸的: She's a rather plain child. 她是个相貌平庸的女孩。