Close, but not identical
The thesaurus is a very handy tool: If you’re puzzling over a word that conveys your exact meaning, or trying really hard to avoid using a commonplace word, the thesaurus gives you an instant list of options. But, while many of the words in the thesaurus can be plausibly subbed in for one another, oftentimes they don’t have the exact same thing. Here are some familiar pairs of words you might think have the same meaning, but don’t quite.
Here’s an example of two words that overlap in certain ways but aren’t synonyms at all: Both “stalwart” and “stubborn” describe a state of being unmovable. Whereas “stalwart” has a positive connotation (someone who is stalwart is steady and reliable), “stubborn” connotes a negative judgment (being stubborn implies some level of ignorance along with the steadiness).
Some people say “obtuse” when they mean “abstruse,” and this is unfortunate because “obtuse” is an insult: it means dim-witted. By contrast, “abstruse” refers to something that is difficult to understand in general. To put it another way, just because you have trouble understanding an abstruse concept doesn’t mean you’re obtuse.