it
Distinguishing between the pronouns it and that is undoubtedly one of the hardest concepts for anyone learning English. The differences are so nuanced that it's difficult even for a native English speaker to explain them without imagining those pictures of physics calculations you sometimes see Albert Einstein standing in front of.
Since the word it has more than one usage, we first need to distinguish three types.
1
dummy it
This is the so-called DUMMY SUBJECT you see in it's raining or it's midnight. In this function, it responds to a rule that in English, EVERY SENTENCE MUST HAVE A SUBJECT, and if there is no logical subject, then we use it. In other words, we can't look out the window and say "Is raining!" We need a subject. But what subject? The sky's raining? The clouds are raining? No, the fact is that there is no logical subject. We're just referring to the situation. But grammatically, we have to have a subject, so we use it: It's raining. However, this isn't the it I describe in this page.
2
idiomatic it
The use of it in idioms. For example, That's it meaning THERE'S NO MORE of something, or I've had it! meaning that YOU'VE HAD ENOUGH of something and are about to lose your temper. This type of it is normally untranslatable on its own and the entire phrase has a special meaning. For instance, in the expression That's it, the word it basically stands for all there is. But in the second idiom, it refers to how much you can tolerate.
This page doesn't deal with this type of it either.
3
pronoun it
The third usage of it is the subject of this page — the use of it as a pronoun. For example, when you're pointing at a watch in a store, and don't know whether to say I'd like to see it or Id' like to see that. Or when you're posting a photo of your pet online and don't know whether to say This is my cat or It's my cat. So the subject of this page is really the choice between this/that and it; or in the plural — these/those and they.
What's a pronoun?
A pronoun, as the name implies, is a word that stands for a noun. For example, he is a pronoun that can stand for a singular male person:
Robert's my father. ⇒ He's my father.
In the above example, we see that the pronoun he can be used to refer to a singular male - my father. Pretty easy, right? When talking about people, it's easy to work with pronouns because there's only one word that refers to a singular male - he, and one that refers to a female - she. However, the difficulty comes when we're dealing with things and situations because there are two sets of pronouns that can stand for them- it and that/this in the singular, and these/those and they in the plural:
It's my scooter -vs- That/This is my scooter.
They're my books -vs- Those/These are my books.
Beginning English learners may not see any difference between the above sets of statements. But the problem is that the pronouns have different features that don't make them completely interchangeable. Below, I'll explain these features and hopefully clear up the confusion.
1 It is definite
What does this mean? As you probably already know, you can't start a story with the words This morning, I saw the jogger… unless the listener knows who the jogger is. The article the makes the jogger DEFINITE: It makes him a specific jogger who the listener knows about because you've previously mentioned him or you both see him running past your house every day, etc.
It needs a referent...
In the example above, the definite phrase the jogger has a REFERENT: a specific person that both you and the listener(s) associate with this person. When there is no referent — for instance, when we first mention someone who the listener isn't familiar with — we normally use the indefinite article a(n), or in the plural, no article or some. This is how we establish them as the referent. In other words, we kind of introduce them and say, for example, This morning I saw a jogger/(some) joggers... After this "introduction," we can call him/them the jogger(s) for the rest of the story because now, it's clear to everyone who we're referring to; which jogger(s) we mean. We have a referent!
Well, it (and they) works much the same way as the. It needs a referent — something definite that the listener can associate it with. However, as we'll see below in (2), as a pronoun, it is a very weak word — too weak to establish something as a referent. In other words, we can't use it to "point" at something and introduce it as the topic of conversation. We need a stronger pronoun that can point something out and set it as the referent.
How do we establish a referent?
When we want to refer to something and set it as the topic of discussion, we need a pronoun that can "point" to it. The pronouns this, that, these, those are called DEMONSTRATIVE pronouns for a reason; the word demonstrative is made up of Latin elements that mean to point out, and that's exactly what the pronouns this, that, these, those do — they point to something and say This is what I'm going to talk about now ⇒ this is our referent.
In summary, when we refer to something for the first time, we first point it out with one of the demonstrative pronouns this, that, these, those, and from that point on, we can call it it (or plural they).
This is a letter I've written my boss to let him know I'm taking another job. Would you mind reading it and telling me if it sounds ok?
Did you notice the sequence? First the letter is introduced with this, and then referred to again with it. Logically, if someone approaches you with a sheet of paper and you don't know what it is, it doesn't make sense to call it it. Starting a conversation with It's a letter I've written would sound unnatural unless the listener is already reading it, or is looking at you with a puzzled look as if to ask What's that?, or actually asks you What's that? or in some other way activates or "points out" the letter. In other words, the letter has to somehow be activated in both your minds, at which point it becomes the referent in your discussion.
Also note that the sequence is the same when asking about something. You first ask What's that? and that is enough to make it the topic of conversation. And if you think What's that? is complicated in English, be glad you're not learning French:
One of the most common mistakes I see online is when English learners post a picture of their pet on social media with a caption like It's my cat. Native speakers look at a post like this and wonder… Who asked? because it looks like a response to the question Who's that? Again, the correct way to introduce someone or something is with a demonstrative pronoun: This* is my cat.
Similarly, They're my cats sounds as unnatural as It's my cat because they, like it, needs a referent. The correct plural form would be These are my cats. You can introduce people and things with these and those, but not with they.
___________
*Things that you post online or in a chat are most commonly referred to with this/these, not that/those.Cryptic It
As we saw above, the usual order is to point something out as the topic of discussion using a demonstrative pronoun like this, that, these, those, and then refer to it as it thereafter. Right? Otherwise the listener will have no idea what you're talking about. However, using it without first pointing something out is a common device in conversation when you actually want someone to ask you what you're referring to as a sort of "cryptic" conversation starter. [To be cryptic is to be mysterious]
[Robert comes down to breakfast and joins his wife at the table]Robert: It's strange.
Linda: What?
Robert: Nancy's been away at school for three months,
and every morning when I'm coming down the stairs, I
still expect to see her at the breakfast table.
Linda: The same thing happens to me.
Here, Robert knows that the statement It's strange sounds cryptic and is anticipating that his wife is going to ask what he's talking about. The thing is, he's doing this on purpose because he wants her to ask what he means so he can elaborate. In other words, he wants to talk about his daughter and chooses to start the discussion by leading his wife into the discussion by cryptically alluding to the topic of conversation.
2 It can't be emphasized!
In an earlier form of English, we had the neuter pronoun hit which had a short, unstressed variant 'it. This unstressed variant is the grandfather of our present-day it. So by its very nature, it is a weak, short, unstressed pronoun. That's why in modern English, as a pronoun, it can't be used in any context that requires emphasis — even the slightest emphasis. So what happens when we need to emphasize it? We simply replace it with that/this since they can be emphasized.
For instance, let's say you're at one of those Japanese places where the food comes around on a carousel. You don't know the name of anything, but you see something that looks good and ask your friend to grab it for you as it passes in front of her. She reaches for the wrong plate. You point at the one you want and say No, I want that. Here you can't say I want it because stressed it doesn't sound natural.
When you finally get the right dish, you taste it and wish you'd picked something different. You put it aside and look to see what else is coming. You grab a different plate, take a bite, and your friend asks, How's that? You smile and say Now this, I like!
Again, you can't say Now it, I like because in order to contrast the new dish with the old one, you would need to use emphasis, and, again, it can't be emphasized.
This is another reason why it doesn't sound natural in introductions. Above we saw that when we introduce a pet, for instance, we normally put some emphasis on the word this and say Thìs is my cát. Compare this to Ịt’s mỵ cát.. A slightly emphasized this draws the listener's attention to the cat in the picture. An unstressed it doesn't really point to anything in particular — it's too weak.
3 It keeps the topic going
When we establish a referent in a conversation and refer to it with the pronoun it, it continues to be that referent until the subject changes and a new referent is introduced. In other words, you can string an endless number of comments and questions about the same referent using it, but if you use that, it sounds like you're talking about something different; changing the subject.
For instance, in this scenario, your friend is looking wide-eyed at your beautiful new car and you say…
You: I bought it yesterday.
Friend: It's gorgeous! How many miles does it have?
You: It's brand new — zero miles.
Friend: You'll need insurance.
You: 🚫That's already insured…
If you said That's already insured, your friend would wonder, What's insured? because that is normally used to change the referent by pointing at something different, so it would sound like you're talking about something besides the car now. The correct response is It's already insured because it is already the established topic of conversation: the car.
However, sometimes, even when it is the obvious choice according to the natural flow of a discussion, the speaker may choose to replace it with that in order to emphasize it:
You: What do you think of my cake?
Friend: That's delicious!
Here the friend could've responded with a neutral It’s delicious. However, he's referring to the cake emphatically, so he can't use it. As we saw above, it is too weak a word to emphasize, so we replace it with this or that when we need to stress it.
