There are tons of resources out there that list commonly misspelled words, including this fabulous Oatmeal poster and this great Grammar Girl book (which is on my Christmas list because I'm so fascinated by language). So I'm not going to list hundreds of words here that you should know how to spell. I'm just going to list five that I see all the time that should definitely be committed to memory.
- Lose and loose: I cringe when I see these words used the wrong way. If you struggle with this, say your sentence out loud before hitting the send button; it should help you realize if you've misspelled lose. The word loose is only used as a verb when you're referring to releasing someone from their bonds. It is usually an adjective, as in Lindsay's pants are really loose. Don't ever use it in phrases like We're going to lose the game or I frequently lose my reading glasses.
- Lightning and lightening: The only time the word lightening is correct is when you're describing the process of actually making something lighter, such as lightening your hair or lightening someone's load. Otherwise, the word lightning should be used, even as an adjective in a phrase like lightning-fast shoes.
- Your and you're: This is probably the most misspelled pair of words of all times, and it shouldn't be. Just remember: Your shows possession. Phrases like Put on your coat or Where is your favorite restaurant? use it correctly. You're is a contraction for the words "you" and "are," and it is used correctly in the phrases You're a wonderful father and I know you're looking forward to this. Writing your welcome is never correct unless it precedes "mat" or "home party."
- Who's and whose: This word pair is very similar to your and you're. Remember that whose is a pronoun that shows possession. For example, you would say Whose dirty socks are hidden under the couch? or Whose dog is barking at midnight? The word who's is a contraction, usually for the words "who" and "is" but sometimes for the words "who" and "has." You use this in phrases like Who's coming to dinner tonight? and Who's picking up the dry cleaning?
- Definitely: I have to admit, when people turn this word into the word defiantly, I have to laugh. The problem comes when people spell it with an "a" instead of an "i." If you often misspell this word, practice saying it the way its spelled instead of as "defi-NAT-ly." Or just commit it to memory. I've had to do this with the word "summit," because for some reason I always want to add an extra "t" to the end.