This is the 2676th most frequent Chinese word.
不难
Not difficult.
Used as a predicate to describe the ease or difficulty level of a task for someone.
这道数学题对他来说不难。
This math problem is not difficult for him.
Used within a clause to indicate a straightforward nature of an activity given certain conditions.
发现答案并不难，如果你仔细观察。
Finding the answer is not difficult if you observe carefully.
Used in an explanatory manner to stress that an activity, contrary to general belief, is not hard.