These three expressions are quite similar in English and often confuse learners.
Yes, in terms of meaning, these three words are very similar. All of them talk about the reason for somebody’s action.
But if we check what type of word they are (especially “Because” and “Because of”), you will find that:
Because = Conjunction
Because of = Preposition
This means that even though they have the same meaning, you have to use each of them this way:
Because + S + V
Because of + Noun
So if you say:
1. I will go there because work.
2. I will go there because of I have work.
You will be wrong.
You have to change them to:
1. I will go there because of work. = OK
2. I will go there because I have work. = OK
If you remember what type of word they are and the different pattern on how to use each of them, they will be easy enough.
Of course you also need to practice them so you won’t mix them up while speaking.
When it comes to the expression “That’s why,” the word “why” is actually part of a Noun Clause.
You should use it like this:
That’s why + S + V.
Is this the same as how we would use “Because”?
Please take a look at this example. This example is right:
I forgot to bring my lunch. That’s why I’m going to the office cafeteria. = OK
It’s very easy and common for learners to think that “That’s why” is the same as “Because.” But in fact, if you substitute the word “Because” in our example above, you will get:
I forgot to bring my lunch. Because I’m going to the office cafeteria. = X
The sentence becomes wrong. This means that “That’s why” and “Because” are used in the same pattern, but they don’t mean the same thing.
Actually, “That’s why” is closer in meaning to the word “So.” If you substitute “So” in our example above:
I forgot to bring my lunch. So I’m going to the office cafeteria. = Ok
I forgot to bring my lunch. That’s why I’m going to the office cafeteria. = Ok
Please remember this meaning of “That’s why” so you can avoid making a mistake.
Finally, the expression “That’s why” can also be used alone:
A: Why do you need to go to the cafeteria?
B: I forgot to bring my lunch, that’s why.
- Or –
A: I wonder why there are so many people at the park today.
B: It’s a holiday.
A: Oh, that’s why.
Hope you learned something!