“难理解”的英语可以翻译为：indigestibility ...

这对那些对它一无所知的人来说可能显得很难理解.This might seem very perplexing to those who know nothing about it.这本科技书里的一些概念很难理解.Some ideas in this science book are hard to lay hold of.细菌生物学有时会很难理解.The biology of bacteria can be quite hard to ...