*clears throat*

Well, you see, a nerd is a more general term for a certain kind of person with a certain variety of interests, such as math, fantasy, and sci-fi. Nerds often enjoy embracing the weird, and they typically get ecxited when talking about their interests. There are many (untrue!) steryotypes about nerds, such as that they all wear glasses. Some nerds like some "nerdy" things but not others, like they might enjoy D&D but not school. This definition, however, is overly simplified and whether someone is a nerd or not depends on numerous variables.

A geek, on the other hand, is more specific but, at the same time, broader. A geek is someone who has an interest in a particular topic, i.e. ancient history, baking, or Harry Potter, and they like to "geek out" about this subject. So, how does this differ from a nerd, you may ask? A geek is interested in one specific topic which doesn't need to be "nerdy" at all, where as a nerd often likes a set of several kinds of things which are the ones that are considered nerdy.

Thank you for listening to my lecture *bows* 

Saffron is telling me to grow a cod! Oh my cod! 

While the terms can be used interchangeably, I think a nerd usually refers to a more introverted or reserved person, who usually enjoys academic subjects (such as math or science). Geeks are more open about their geeky interests, which are usually related to a particular fandom or fandoms (such as Star Wars or Dungeons and Dragons). Nerd is occasionally used as a derogatory term, due to the sometimes quirky nature of a nerdly person. 

Hmmm... I guess I would be more of a geek than a nerd, according to Win's definitions, 'cause I'm in like a thousand fandoms which I'm obsessed with. But I'm probably also a nerd too XD