Nerd (noun)

1. A person who is intellectually curious, socially awkward, and often obsessed with a hobby or subject.
2. A person who is highly knowledgeable and skilled in a particular field but is often viewed as socially awkward or lacking social skills.

Origin:

Slang, first recorded in 1951, american english, probably an alteration of 1940s slang nert, itself an alteration of nut, meaning "a crazy or eccentric person".

Examples:

1. He's such a nerd, he spends all his free time reading science fiction.
2. She's a total nerd when it comes to computer programming.
3. He's a history nerd, always reading books and talking about ancient civilizations.
4. She's a nerd when it comes to her passion for astronomy and spends hours observing the stars.
5. He's a bit of a nerd, always studying and getting good grades.