In the meaning in which the phrase is usually understood, to share a common interest is indeed a tautological because it means that some people both have an interest in something that they both are interested in: both share and common indicate that the object is applicable to all subjects involved.

In that case, I would indeed say

it’s because they have an interest in the world.

They

have a common interest. If that is true, why do we love them so much?

On the other hand, if I invite individual in a group to share some of their personal details with the group, they are certainly invited to list their interests or hobbies. If individual interests are not applicable to others in the group, or if those interests are out of the ordinary in general (see example in my comment to Susan), it would be correct to say they are sharing uncommon interests. If their interests do apply to the rest of the group as well, one could similarly state (without it being a tautology) that they were sharing common interests.

This would involve a different meaning of the verb to share altogether though.

In the same way, we want to express how common (or usual ) interests are that two or more individuals share, the statement They

share a common interest.

If someone is doing so, should he or she be read as “they are both interested in something that is very common, like pop music. In that case, there is also no tautology.

TLDR:

So, if “share” means “to tell something”, or “common” is understood to mean “usual”, there is no tautology. In the general sense of “they share an interest” meaning “they have a common interest”, I would see “they share a common interest” as in a

tautology.

How does the fact that she states one of my children means she has more than one child?

If the sentence were different from the one described earlier we would have read it differently. Is she referring to the one time this particular child was ill? One of my children in this refers to any of them.

So, the most likely reading is that there has been one instance where a child of hers has been ill – and that was like the situation she described.

If she’s had any other children that’ve been ill, but not like that, she found she had the same child and the same job,

instead of the same child.

In that case, a younger son may have been ill too, but it was not “like that” – or at least not so much “like that” that the writer truly feel it should be mentioned.

If you buy the wise people and buy them miserable means that by spending money, you make them wise.

In this case, what you buy them is education.

How do I buy my kids clever?

No matter

how much money you spend on education, books or training, if your kids aren’t smart, no amount of buying stuff will make them smart.

What is the grammatical construct that is used in Edwin Ashworth’s answer?

If you buy the wise people and buy them miserable means that by spending money, you make them wise.

In this case, what you buy them is education.

How do I buy my kids clever?

No matter

how much money you spend on education, books or training, if your kids aren’t smart, no amount of buying stuff will make them smart.

What is the grammatical construct that is used in Edwin Ashworth’s answer?

What first said to me that would go stoic?

Is the reference to stoicism too heavy? Do you feel like this is a character trait?

What’s another way to react without emotion?

Can you simply say that you are untouched by his departure, or

He leaving leaves me cold?

Is there no one word to add to

the last option?

What first said to me that would go stoic?

Is the reference to stoicism too heavy? Do you feel like this is a character trait?

What’s another way to react without emotion?

Can you simply say that you are untouched by his departure, or

He leaving leaves me cold?

Is there no one word to add to

the last option?

What first said to me that would go stoic?

Is the reference to stoicism too heavy? Do you feel like this is a character trait?

What’s another way to react without emotion?

Can you simply say that you are untouched by his departure, or

He leaving leaves me cold?

Is there no one word to add to

the last option?

What does a simple dictionary say? Where can I purchase Oxford online?

If you used form as a noun then it must always stand. This

is true under nominative. Afterwards, the numer is automatically countable. 2 Style, design, and arrangement in an artistic work as distinct from its content:
these videos are a triumph of form over content

-2. A particular way in which a thing exists: essays in
book form energy in
the form of light?

The customary or correct method or procedure:
an excessive concern for legal form and precedent

-7. The state of a sports player or team with regard to their current standard of play:
they are one of the best teams around in current form

-7. 2 A person’s mood and state of health:
She seemed to be in good form

-7. 3 British INFORMAL A criminal record:
they both had form

The only use that is confusing, because one example uses form as a mass noun, the other as a countable noun, is meaning 2. How does the body of form appear in a given text?

In the first instance in your text, the sentence follow exactly the example given: in book form versus in electronic form. Where do the articles of an article come from?

In the second instance of the form in your text, when the reference is not to electronic form in a general sense but it is about a specific shape in which information is to be presented? The simple transformation into electronic form as mentioned earlier is no longer sufficient to describe it, we need now to specify a specific electronic form. We can conclude that there are other forms that may be electronic, but can not be processed by a computer.

When we describe the way in which a thing appears or exists, we only use form as a mass noun when we refer to that way of existence. Literature usually appears in book form.

Like Wikipedia, when we talk about a specific instance or type of that way of existence, we use it as a countable

noun: Paper encyclopaedias would not always be portable book forms.

In the form of, ” form in the construction by, ” is always countable”.

How can I know who is in which position or country?

Does strictly speaking they don’t convey the same meaning? In practice your first sentence is often used for the second. We have become accustomed to situations where a ‘first sentence’ means’second sentence’.

I believe that x does not equal y means that you actually hold a belief about the inequality of x and y.

If x equals y then you don’t share your belief.

I know that x doesn’t equal y. Is it easier to add another

• verb than believe?

I have actual knowledge that x and y are not the same. Are they not the same? Certainly I can show you facts to support this.

• I don’t know that x is equal to y.

Why is x equal to y? Is it possible to possess a knowledge to to the contrary? Even then, we are unaware, of how to know.. Can you tell me if x equals y?

Languages or mathematics, are the same! As Edwin Ashworth points out, there is a lot more to these kind of constructions than meets the eye (and a lot more than I would be willing to explain here). I suggest the article that Edwin linked to (Just in case the comments deteriorate, I include the link here as well).

Rather, many people will say ‘don’t believe x

equals y’.

I believe

that x does not equal y. I have already answered yes. I will continue again.

It is also common sense to use this vocabulary in English – although the usage is often used by some misunderstandings. In particular in theological discussions, it is common that the claim:

I don’t believe in the existence of the deity X.

(1) is wilfully ignored

as I believe that deity X does not exist. (2)

in which case the straw man argument can become the basis of a straw man argument if the speaker actually meant to make a distinction between agnosticism or so-called weak atheism (1) and so-called “strong atheism” (2).

So, depending on context, the two sentences may mean the same, but be aware of situations where a strict interpretation is better suited – in which case one can make a very clear distinction in meaning between the two phrases.

Does strictly speaking they don’t convey the same meaning? In practice your first sentence is often used for the second. We have become accustomed to situations where a ‘first sentence’ means’second sentence’.

I believe that x does not equal y means that you actually hold a belief about the inequality of x and y.

If x equals y then you don’t share your belief.

I know that x doesn’t equal y. Is it easier to add another

• verb than believe?

I have actual knowledge that x and y are not the same. Are they not the same? Certainly I can show you facts to support this.

• I don’t know that x is equal to y.

Why is x equal to y? Is it possible to possess a knowledge to to the contrary? Even then, we are unaware, of how to know.. Can you tell me if x equals y?

Languages or mathematics, are the same! As Edwin Ashworth points out, there is a lot more to these kind of constructions than meets the eye (and a lot more than I would be willing to explain here). I suggest the article that Edwin linked to (Just in case the comments deteriorate, I include the link here as well).

Rather, many people will say ‘don’t believe x

equals y’.

I believe

that x does not equal y. I have already answered yes. I will continue again.

It is also common sense to use this vocabulary in English – although the usage is often used by some misunderstandings. In particular in theological discussions, it is common that the claim:

I don’t believe in the existence of the deity X.

(1) is wilfully ignored

as I believe that deity X does not exist. (2)

in which case the straw man argument can become the basis of a straw man argument if the speaker actually meant to make a distinction between agnosticism or so-called weak atheism (1) and so-called “strong atheism” (2).

So, depending on context, the two sentences may mean the same, but be aware of situations where a strict interpretation is better suited – in which case one can make a very clear distinction in meaning between the two phrases.