宅男 is NOT nerd. 宅男 means people who rarely get out from their house. 宅男 emphasizes that people do anything in their house. Whereas nerd emphasizes that people stay far away from the society, they have their own way to learn things. For example, if a person always goes to the library to learn things, we can call him nerd, right? But we CAN'T call him 宅男, because library is not where he lives. In chinese, we call people who always read books 书呆子. It means a guy getting everything from books and he doesn't do anything but reading books. Normally 书呆子 is NOT a good word.

nerd多指书呆子，有种萌萌哒的感觉。

英文里”geek“的一色比较好的含义。有人听到”geek“的时候，想到比较聪明，喜欢科技的人。 但是我觉得负面的含义跟中文的含义有些类似，我们也想到内向的人或者不会跟女人谈谈的男人。 :D 我觉得大多数的我认识的美国”geeks“不是害羞自称”geek”。 （无关：我的中文憭不憭？我的语感还是不太好。。。）

我认为宅男 跟英文里的“geek”更相似，更加偏向于在家里打电脑游戏的男生。没有绝对的好和不好。但我不知道英文里“geek“是好的意思吗？

一个名词没什么所谓好或者不好的。只是一种指代，因为宅在家里太久了所以被叫做“宅男”或者“宅女”。 另，nerd和宅男根本不是同一个意思。