a.

1. （指任務）需要精力或技術的，困難的[+to-v]
   It's very difficult to swim across the Yangtze River.

   游過長江很難。

   Mathematics is difficult for some students.

   有些學生覺得數學困難。

2. 難相處的，不隨和的
   Mary was a very difficult child.

   瑪麗過去是一個很難相處的孩子。

3. 艱難的，難熬的
   The most difficult days are over.

   最困難的日子已經過去了。

adj.

1. needing much effort or skill to accomplish, deal with, or understand.
2. not easy to please or satisfy; awkward.