in·tro·vert
/n., adj. ˈɪntrəˌvɜrt; v. ˌɪntrəˈvɜrt/ Show Spelled [n., adj. in-truh-vurt; v. in-truh-vurt]
noun
1. a shy person.
2. Psychology: a person characterized by concern primarily with his or her own thoughts and feelings, opposed to extrovert .

nerd
/nɜrd/ Show Spelled [nurd] 
noun Slang.
1. a stupid, irritating, ineffectual, or unattractive person.
2. an intelligent but single-minded person obsessed with a nonsocial hobby or pursuit