The list of commonly misused words is extensive. There are several that tend to be most commonly misused and deserve inclusion in a short list. Sometimes these misused words are simply the result of spelling errors, at other times, misused words can significantly change the meaning of a sentence.
People tend to get into trouble with words using apostrophes. Many people include apostrophes when changing a word to plural form. For example, if one wants to pluralize friend, the correct plural is friends. The incorrect form is friend’s. The apostrophe in this case implies possession.
Apostrophes are used for two purposes: to indicate possessive form or to join two words together like do not into “don’t.” However, two of the most commonly misused words are “its/it’s." This is because the “it’s” does not indicate possession. Instead it is a contraction of the words “it is.” “Its” is possessive and a relative to his, hers, yours, theirs, and ours. It helps to think “his, hers, its,” to avoid misuse.
Another set of commonly misused words are “there, there’s, they’re, their, theirs.” “There” is a place, like “Ooh let’s go there for dinner.” “Their/Theirs” indicates possession, as in “That is their car,” or “The car is theirs”. Like “its,” “theirs" does not require an apostrophe. “There’s/They’re” are both contractions. “There’s” joins “there is”, and “they’re” joins “they are.”
“Who’s/Whose” also are commonly misused words. “Who’s” is a contraction of “who is.” “Whose” indicates possession, as in, “Whose shoes are these?” “Your/You’re” are also subject to the same confusion. “Your” possesses, like “your shoes” and “you’re” joins “you are.”
Other commonly misused words often sound similar but have very different meanings, like “assure/ensure/insure.” Assure means to guarantee something, while ensure means to make sure of something. Insure really relates to insurances and should not be used in place of the other two words.
People often turn “accept/except” into commonly misused words. To accept something is to tolerate it or agree to it. Except is used to exclude something, like “I like all flavors of ice cream, except banana.”
Another set of commonly misused words is “affect/effect.” It helps to remember that an effect is a result of something, as in cause and effect. Affect means to change something or to alter something, such as, “His speech affected the audience deeply,” or “He noticed he had affected the outcome of the experiment by forgetting to turn off the lamp.”
Other commonly misused words are “than/then,” “farther/further,” proceed/precede,” and “foreword/forward.” The list extends far beyond these examples. A good style manual, like Strunk and White’s Elements of Style may be helpful in correcting word usage. One can also find many books devoted specifically to commonly misused words which can help clear one’s writings of mistakes.