If you describe someone's behaviour or feelings as understandable, you think that they have reacted to a situation in a natural way or in the way you would expect.
His unhappiness was understandable.
他的不高兴是可以理解的。
If you say that something such as a statement or theory is understandable, you mean that people can easily understand it.
Roger Neuberg writes in a simple and understandable way.
罗杰·纽伯格的作品简单易懂。