艰深的

abstruse; difficult to understand

1. 这些艰深的学术讲演他不能完全听懂。
   He could not fully understand these involved scholarly lectures.
2. 他为什麽非得用这麽艰深的语言说话呢？
   Why does he have to wrap it all up in such complicated language?

深的英语翻译：