Name: 文法：如何正確使用IF和WHETHER？ (Grammar: How to use IF & WHETHER properly)
Uploaded: 2021-01-14T05:41:30.000Z
Duration: 6 min 58 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Hi again. Welcome back to www.engvid.com. My name's Adam. Welcome again. Today's lesson

頻率副詞

is a grammar lesson, and this is a question that I am asked often. What is the difference

between "if" and "whether"? Okay? It's a very good question. It's pretty simple, straightforward,

but we're going to look at both of these in relation to each other.

First of all, let's make sure everybody understands "whether" is not spelled the same as "weather",

like sunny, raining. This is about rain, sun, snow, wind, temperature; this is similar to

So, in some situations, "if" and "whether" are interchangeable, but the best way to not

make a mistake, not to mix them up in the wrong context is to always use "if" for conditionals;

always use "whether" when you're talking about two alternatives, two choices. Okay? You'll

When they can be interchanged. First of all, when they are used as noun clauses, means

they can be the object or the subject of a sentence, they can mean the same thing. But

again, avoid using them the same if you don't want to make mistakes. "Do you know if Dan

is coming?" Do you know what? If Dan is coming. "Do you know whether Dan is coming?" In this

case, they basically mean the same thing. Yes or no: is he coming or is he not coming?

You could add the "or not?" here: "Do you know whether Dan is coming or not?" But the

word "whether" already gives you a choice between yes or no in this particular case,

so this is not necessary. It's understood. Okay?

Now, let's look at these two sentences: "I don't know if the exam is on Friday or Saturday.",

"I don't know whether the exam is on Friday or Saturday." So here, we're looking directly

at a choice. When I use "whether": "I don't know whether the exam is on Friday or Saturday."

So again, you have two options when you look at "whether". Friday is one option, Saturday

is another option. The problem here is if you use "if", "if" is not limited to two options.

"I don't know if the exam is on Friday or Saturday, or if it's next week sometime."

So here, although they seem to mean the same thing, the "if" gives you other options that

the "whether" doesn't. "Whether": one, two. "If": one, two, or something completely different.

So if you want to avoid making this mistake, use "whether" for the choices, use... Save

"if" for when you have your conditional sentence. Now, what is a conditional sentence? A conditional

sentence is using "if" as an adverb clause. There's a condition. If "A" happens, "B" will

happen. Okay? One thing needs to happen for the second thing to happen, that's the condition.

So: "Let me know", oh, sorry. I forgot this word, here. "Let me know if you're coming.",

"Let me know whether you're coming." In this case, they're both okay. "Let me know whether

Now, what's the difference between: "Let me know if you're coming", "Let me know whether

you're coming or not"? If you are coming, yes, let me know. This is a conditional. If

this is true, do this. "Let me know whether you're coming or not." If you're coming, let

me know; if you're not coming, let me know. So in this case, both apply. Okay? So, again,

use this to... The condition. This is the condition, this is the result. Here, this

is going to happen regardless. So we're going to look at this in a second in more detail.

"I'll come over if you want me to." If you want it, I will do it; if you don't want it,

I will not do it. So this is the condition. If you want me to, I'll come over. This is

the condition, this is the result. So your best option is to always use "if" with conditionals,

use "whether" to talk about two alternatives.

Now, the other common use of "whether" is to mean "regardless". Doesn't matter what

happens, regardless of the situation, here's what I want you to do. "I'm coming over whether

you like it or not." Okay. "Whether you like it or not" means if you like it, I'm coming

over; if you don't like it, too bad, I'm coming over. So this verb is going to happen regardless

of this situation. Okay? So that's when we must also use the "or not". Remember here,

I said "or not" can come out because it's understood here. Here are your two options.

Here, it's not about options. Here, it's about saying something is regardless. Doesn't matter

what you like, what you don't like - I'm coming over. Okay? "I'm coming over if you like it",

it means: you like it, I'm coming; you don't like it, I'm not coming. Okay?

So: "whether", to talk about regardless, you must have the "or not". To give the options,

you don't need the "or not". If, in a noun clause-means this situation-is the object

of "know". Know what? If he is coming. Yes or no. Here, it's a conditional. So first

of all, you must understand: is it a noun clause object or is it an adverb clause condition?

So, to avoid making mistakes, especially in written English: use "if" for conditionals,

use "whether" for alternatives or to mean "regardless". Okay? It's a little bit tricky,

but when you see more examples, it will become much clearer.

So if you want to see more examples, come to www.engvid.com. There's a quiz there that

will test your understanding of this. Ask any questions you have on the comments section.

Don't forget to subscribe to my YouTube channel. Come back. I'll see you again. Bye.