Spell check lets you add words to your custom spell-check dictionary that aren’t found in the standard dictionary. Once added, spell check skips over them, accepting their spelling as is. If you use unusual words a lot – those that may be common in your business or with a particular client – then this feature is especially useful.
But it’s also easy to inadvertently add words that are, in fact, spelled incorrectly. It may be that at the moment the spelling - however unusual - works for whatever it is you are doing, or that you’re working so fast that you accidentally click “add word” when going through the spell-check process. (This is easy to do when spell checking a long document.) Once added, however, these words may never be caught by the spell checker again. To avoid this problem you need to erase your custom dictionary every few months. This will allow the spell checker to catch those misspelled words in the future.Here’s how to do it:
Remember, spell checks do not distinguish between homonyms - words that sound the same but are spelled differently, like bare and bear, their and they’re, current and currant, and gorilla and guerrilla (that last mistake is more common than you’d think). And they aren't mind readers either. Spell checkers don't know you meant to type the word "same" when you typed "sane," which is a typo I just caught while writing this post.
Spell checkers are important tools, but they are not substitutes for good, old-fashioned proofreading.