Two years? I didn't know it took that long to write your book.
I heard that the book won many awards.
That is interesting.
Could you please give me that book?
That said, it is not surprising that the word is so common in the English language. We even used it twice in our previous sentence!
What can confuse writers is not how common "that" is, but how easy it is to replace it with words such as "which" or "who". Such replacements are often incorrect, which is why it is crucial that we know how to properly use "that", as well as when not to use it at all.
In writing, it is important:
Some of the most common traps in English grammar are relative pronouns. They connect a noun or pronoun to a clause or phrase. Many English learners are taught that "which" is used for nouns that represent objects, and "who" is used for people.
The reality is much more complex. "That", "which", and "who" can sometimes be used in the exact same contexts referring to the same nouns. However, the meaning of the sentence will change if "that" is placed incorrectly instead of "which" or "who".
The main difference between "that" and "which" is in restrictive and nonrestrictive clauses.
A restrictive clause is a part of a sentence that provides essential information. We cannot take it out of the sentence without affecting its meaning.
This is the new car that we bought.
The bold part above is a restrictive clause. If we take it out, we lose an important part of the meaning.
Some more examples of restrictive clauses:
Students who practice daily are likely succeed.
He's the man that won the swimming competition.
That's the house which we painted.
A nonrestrictive clause provides information that can be left out without affecting the meaning of the sentence.
Bob, who sits next to us, is a good husband.
The bold part above is a non-restrictive clause. If we take it out, we do not lose an important part of the meaning.
Some more examples of nonrestrictive clauses:
Tammy, who works with my sister, is working out daily.
He went on a trip to Sweden, which is in Europe.
Grandma, who is always happy to see you, offered to bring you some soup.
"Which" is used at the beginning of nonrestrictive clauses. This means that it does not restrict the noun it relates to in any way. When surrounded by commas, "which" serves to add new information to the sentence.
The chairs, which were produced in 1898, were sold to a French family.
In the sentence, the writer informs us that the chairs were sold to a French family and, in the same sentence, adds information about when they were made. This new information does not necessarily relate to the fact that the chairs were sold to a French family.
Salt, which used to be a precious good, is one of the cheapest ingredients.
These two dresses, which were designed last year, are very popular.
"That" generally limits the noun it refers to. This is also known as a restrictive clause because the part of the sentence which begins with "that" restricts the noun it relates to in some way.
Words that come from Latin are usually difficult to pronounce.
In this sentence, "that" is used to refer only to those words that come from Latin and not all words in general.
Businesses that have more than five employees pay higher taxes.
Cars that are made by Renault are very popular in this country.
An easy way to distinguish between "that" and "which" is to see what happens if the clause is removed. Generally, if you remove a clause starting with "that", the meaning of the sentence also changes.
Movies that come from Latin America win many awards. => Movies win many awards.
The meaning of the sentence changes because we no longer know which movies win many awards.
This is not the case with "which".
The movie "Love", which we watched on Sunday, won the Oscar. => The movie "Love" won the Oscar.
Here, if the take the nonrestrictive clause, which is separated by commas, out, the meaning of the sentence will not change. We still know which movie won the Oscar (although we do not know when the writer watched it).
A well-known rule suggests that "who" is reserved for people both as a relative pronoun and as a determiner. Unlike with "which", English learners know "that" should not be a replacement for "who" regardless of the context. The rule says "who" should only be used when referring to people, whereas "that" is more adequate for objects and subjects.
In other words, you cannot write:
The book who I bought last week is really interesting.
Instead, you can only say:
The book that I bought last week is really interesting.
Still, there are certain contexts where "that" can refer to people, as well. This mostly happens in situations where we do not know the name of a person or simply don't know them personally.
The electrician that came yesterday called.
Do you know the name of the boy that we saw in the supermarket?
Furthermore, "that" can also be used to refer to plural nouns, including people.
People that act that way are annoying.
"That" is not always mandatory in a sentence. Depending on its role, this word can be omitted, especially to avoid long sentences and decrease the word count. For this reason, it is advisable to drop "that" when it is not needed to avoid overusing the same word numerous times in your text.
This can be done when "that" follows a reporting verb such as say, tell, think, know, state, suggest, etc.
We know that Jeremy has two children. => We know Jeremy has two children.
Mom said that we should be home by 8 pm. => Mom said we should be home by 8 pm.
Both versions of these sentences are acceptable in writing.
In addition, you can omit "that" when explaining why something is happening. In such cases, "that" must precede a noun or pronoun.
My parents were so happy that you came. => My parents were so happy you came.
Here "that" helps the writer explain why the parents were happy, which is why it can be omitted.
I am sad that Dan is moving to London. => I am sad Dan is moving to London.
Finally, "that" can sometimes be omitted when explaining "which one?"
I can't wait to watch the movie that Dana recommended. => I can't wait to watch the movie Dana recommended.
"That" can be omitted because "that Dana Recommended" explains which movie I can't wait to watch.
Remember the man that I saw on the train? => Remember the man I saw on the train?
"That" can be omitted because "that I saw on the train" explains which man the writer asks about.
Some more examples:
Where's the book that you borrowed from me? => Where's the book you borrowed from me?
I haven't opened any of the presents that I got for my birthday. => I haven't opened any of the presents I got for my birthday.
I really like the girl that my brother is going to marry. => I really like the girl my brother is going to marry.
Did you find the glasses that you lost yesterday? => Did you find the glasses you lost yesterday?
So to summarize, you can omit "that" in the following cases:
"That" can have various roles in a sentence. In certain situations, "that" is an integral part of a sentence and cannot be omitted. Doing so would make an incomplete and confusing sentence.
For instance, "that" serves as a determiner to point out to an object which is distant.
That painting is by Picasso.
That man is my brother.
It would be grammatically incorrect to drop "that" in such a sentence because it would be incomplete and would not make sense.
Incorrect: Woman is my wife.
Correct: That woman is my wife.
Incorrect: Store belongs to Tommy.
Correct: That store belongs to Tommy.
Incorrect: Way of acting is unacceptable.
Correct: That way of acting is unacceptable.
Incorrect: Kind of analysis is not good enough.
Correct: That kind of analysis is not good enough.
Incorrect: Level of irresponsibility is rude.
Correct: That level of irresponsibility is rude.
Many compound conjunctions make pairs with "that". Compound conjunctions are conjunctions with two or three parts which always go together to connect different parts of a sentence. For this reason, "that" should never be omitted from the sentence with such a compound conjunction.
Incorrect: Maria feels great now she has passed her exams.
Correct: Maria feels great now that she has passed her exams.
Incorrect: I will see you tonight provided I don't have to go to the meeting.
Correct: I will see you tonight provided that I don't have to go to the meeting.
Incorrect: George took a photo so he has a proof of what happened that day.
Correct: George took a photo so that he has a proof of what happened that day.
Parallelism means using components in a sentence that are the same in their structure. In other words, different parts of a sentence need to agree. This rule should be followed when it comes to "that" too.
Sometimes, "that" comes in a pair with another "that", particularly when there are two or more verbs or when the writer is providing two or more pieces of information. It is important none of the "thats" is omitted.
We must write two "thats" in this sentence because we are providing two independent, yet related pieces of information that refer to the subject and verb. Because one clause "the meeting went well" starts with "that, it is logical that the other clause "everyone is happy" does, too.
Incorrect: It was brought to our attention that the meeting went well and everyone is happy.
Correct: It was brought to our attention that the meeting went well and that everyone is happy.