Good writing is all handmade. It’s made of words. Looking up words as you write is a vital step in research. A word choice isn’t apt merely because a word’s formal definition seems to fit. Words are layered with meaning, and the layers need to fit as well. If you write “the final solution to our problem” unaware that “final solution” translates the Nazi euphemism for the Holocaust, die Endlösung; if you write “a supercilious handshake” unaware that “supercilious” derives from Latin words meaning “above the eyelid” (i.e., with a lifted eyebrow), you communicate more and less to your reader than you intend. Sloppy word choice isn’t only a literary sin; it’s confusing. If you choose words with their multileveled meanings in mind, your reader will have a better chance of understanding what you mean—and so will you.