4 More Common and Confusing Grammar Mistakes

- That vs. Which:
First off, “that” and “which”]/i] are pronouns used to introduce clauses in a sentence. Using them allows writers to combine sentences and avoid a multitude of short, choppy copy.

Seems simple enough, right? So why are we so confused? We are confused because we don’t know which word to use. [i]“That” and “which” are not interchangeable, yet people seem to think so.

In order to decide which word to use, you must first determine if the clause in question can be removed without changing the meaning of the sentence. If the clause can be omitted, you would use “which”. If the clause cannot be omitted, you would use “that”.

"The blue ball, which he got for his birthday, was his favorite toy." The blue ball was his favorite toy. In this case, “which” is used because you can remove the clause “which he got for his birthday” without changing the meaning of the sentence.
"The dog that bit the mailman was sent to the pound." The dog was sent to the pound. In this case, “that” is used because “that bit the mailman” tells the reader which dog was sent to the pound.


- You’re vs. Your:
This is one of those common mistakes that can easily be fixed. “Your” is a possessive adjective, meaning it tells us possession. “You’re” is simply a contraction of “you are”.

When deciding which to use, replace you’re/your with “you are”. If it makes sense, use “you’re”.

"I think you’re the best." "I think you are the best." It makes sense, so “you’re” is the correct word.
"Your pencil is sharp." "You are pencil is sharp." It doesn’t make sense, so “your” would be the correct choice.


- Then vs. Than:
Though they may sound the same, then and than have two very different meanings. Than is used for comparison and then is used as a description of time.

"My rock is bigger than your pebble." Since you’re describing a comparison, “than” is the right word choice.
"We would then go right to bed." Since you are describing time, “then” is the correct choice.


- Who vs. Whom:
When to use “who” and “whom” is very confusing to most people; however, learning which one to use when is as simple as knowing when to use “I” and “me”.

Who is a subject, just like “I”. It is the person performing the action of the verb. Whom is an object, just like “me”. It is the person the action is being done to/for.

A great way to remember which word to use is to replace who/whom with “him”. If the sentence makes sense, then “whom” would be the correct choice.

"He left with whom?" "He left with him." Since “him” makes sense, “whom” would be the correct choice.
"Who is going to the concert?" "Him is going to the concert." Since this doesn’t make sense, “who” would be the correct choice.

As always, I hope this helps alleviate any confusion you may have. Please feel free to share your own tips or let us know other words that trip you up.

http://blog.desertrose.net/4-more-common-and-confusing-grammar-mistakes/