难 + 动词
nán + dòng cí
Expressing "difficult" with "nan"
难 in front of a verb means the action is hard or unpleasant to do.
难 + Verb
How it works
难做 (hard to do), 难买 (hard to get hold of), 难吃 (unpleasant to eat), 难看 (ugly).
It's the exact opposite of 好 + verb, and 难吃 / 难看 come from this pattern just as 好吃 / 好看 do.
难 as an ordinary adjective simply means "difficult": 中文很难.
Examples
zhè ge zì hěn nán xiě
这个字很难写。
This character is hard to write.
zhè ge cài hěn nán chī
这个菜很难吃。
This dish tastes awful.
běi jīng de fáng zi hěn nán mǎi
北京的房子很难买。
Property in Beijing is hard to buy.