I love dictionaries. Why? Because words are my tools and unlike the physical tools for carpentry, there are over 250,000 words in the English language. The garage of my brain won’t hold all those words.
Secondhand stores rock for specialized dictionaries. I have dictionaries for Geological Terms, Biology, Art and Artists, Electronics, Music, Commerce, Superstitions, Philosophy, and Science (and at least three slang dictionaries which are their own category of fun).
From The Dictionary of Electronics, I learn that an intrinsic stand-off ratio is formed in an unijunction transistor, where the voltage on the n side of the junction at point A is given by nVb3 where n is the intrinsic stand-off ratio. If you can make sense of that, you’re a better person than I am. But it could be used in a story about an electrical engineer who imagines herself and her husband as an unijunction transistor and the intrinsic stand-off ratio as the distance between them.
There are specialized dictionaries online, but there is something to be said for flipping through a paper dictionary. Sometimes another word can lead to a new train of thought, give you a way to decribe a character, or inspire a scene. There’s no room in my starving artist budget to buy these books new but for a few second-hand dollars, I’ve already had my money’s worth from most of them.