A wonk is someone who studies a subject far more deeply than most people would, and cares about the small details of it. The word started as American student slang for a classmate who worked all the time, and it kept that slightly teasing edge. Its main home now is politics: a 'policy wonk' is a person who knows the tax rules or the health-care plan line by line, and will happily explain all of it to you. The word became very common in America in the 1990s during the Clinton years, when knowing the details was fashionable. Here is the interesting part: 'wonk' is now often a compliment, or at least worn with pride. People call themselves wonks. On the internet you will see 'transit wonk', 'budget wonk', 'grammar wonk'. But it can still sting, because it hints that the person is dull, or lost in numbers and blind to how real people feel. The same sentence can go either way depending on tone. It is informal — never in a formal report about someone. There is also a related adjective 'wonky', but be careful: 'wonky' usually means shaky, crooked, or not working properly, which is a different word entirely.

（政策）專家、鑽研細節的人；書呆子（帶點調侃，但現在也常是褒義）