Let’s look at some commonly-confused pairs of words, and the differences between them.
premiere vs. premier – A “premiere” is the first showing of a play, movie, etc. A “premier” is a high-ranking government officer, sometimes equivalent to a prime minister. The Premier of China decided not to attend the premiere of Taken 2, on account of its suckage.
sympathy vs. empathy – “Sympathy” means feeling for someone, while “empathy” means feeling with someone. If you sympathize with someone’s suffering, you pity them, but if you empathize, you actually put yourself in their shoes and feel a little of what they’re feeling. I sympathized with him for having seen Taken 2, but since I hadn’t seen the film myself, I couldn’t really empathize.
decry vs. descry – To “decry” something is to denounce or condemn it. Obama and Romney have been decrying each other’s policies for months now. Totally unrelated is “descry,” which means that you see something unclear by looking carefully – for example, you might descry Waldo in a picture after a moment of hunting. Unable to descry even a hint of originality in Taken 2, the critic decried its director, its writer, and whoever came up with that breathtaking title.
affect vs. effect – This pair’s especially tricky, since both words have multiple meanings. “Affect” typically means to influence, so if a hurricane affects your travel plans, it means your plans changed because of the storm. “Effect,” on the other hand, is typically a noun, as in “cause and effect.” Watching Taken 2 affected me deeply: its effects included nausea and clinical depression. However, “affect” can also mean to pretend, as in “The girl from Pakistan affected a Norwegian accent.” And “effect” can be a verb, meaning to cause an effect, as in “Our presentation effected a major shift in their policy.”
ensure vs. insure – In general, “ensure” means to make sure, so for instance, you might take good care of your car to ensure it doesn’t break down. On the other hand, “insure” generally means to guarantee against harm, so if you insure your car, you’re guaranteeing that you’ll get repaid if your car does break down. My insurance policy doesn’t refund ticket prices for bad movies, so I’ll just have to ensure that I don’t see Taken 2. But just to make things even more confusing, the dictionary says “insure” and “ensure” can also take each other’s meanings. I wouldn’t recommend it.
What words do you get confused?
My favorite is affect/effect because so many people get it wrong, even when trying to clarify and help. Beyond even all the things you listed, there’s even a clinical psychological definition of “affect.”
“A feeling or emotion,” according to dictionary.com. That’s a new one on me. Cool!