Is "foreign countries" a tautology? [closed]

EDIT: Let me start by addressing OP's explanation of how the question occurred, which was posted after I'd already posted my answer.

As OP writes, an ESL student asked what foreign means in the phrase in many foreign countries. The OP answered that it meant of a country other than one's own. The student pointed out that (1) this would imply that the phrase may be paraphrased as

[1] in many countries of countries other than one’s own,

and the OP thought (2) that this sounds tautological.

As I will now explain, both (1) and (2) are wrong: the original phrase cannot be paraphrased as [1], and, regardless of that, [1] is not tautological.

1. The 'problematic' phrase [1] is not a tautology, but rather an application of an incorrectly stated definition

The 'problematic' aspect of it is already present in the noun phrase

[2] countries of countries other than one’s own

The problem with [1] is not that it's a tautology (which it is not), but rather that it doesn't mean foreign countries. It means something else, as I will now explain.

Consider first just the phrase a country of countries. This phrase has been used to describe actual countries of the world. Some examples:

The United Kingdom is not a single country but a country of countries. It’s made up of four nations: England, Scotland, Wales, and Northern Ireland. (link)

Today, the United States is divided, a country of countries characterized by bitter partisanship, economic decline, environmental degradation and growing social inequity. (link)

Spain is a country of countries, or a nation of nations. (link)

A Country of Countries (a section title from the publication The Soviet Union by Time-Life, 1985) (link)

Other countries that could be considered 'countries of countries' include e.g. the Netherlands and Denmark (as I explain below).

Now let's consider

[2] countries of countries other than one’s own

This is ambiguous as far as whether other than one’s own belongs with the first of the second countries.

An example that would clarify the first interpretation is this:

Suppse there are exactly three countries of countries: the UK, the Netherlands, and Spain. My own country of countries is Spain. Then the other two (the UK and the Netherlands) can be collectively referred to as 'countries of countries other than my own'.

And for the second interpretation, suppose Scottland becomes independent from the UK, so that the post-Scottish-independence UK only consists of England, Wales, and Northern Ireland. If I am from Scottland, I might say that the post-Scottish-independence UK is 'a country of countries other than my own' (because my own country, Scottland, is not a part of this new UK). Similarly, suppose the Ukraine seceded from the Soviet Union, but that the Soviet Union is otherwise intact. And suppose I am a dual citizen of the newly-independent Scottland and of the newly-independent Ukraine. Then I might collectively describe the new UK and the new Soviet Union as 'countries of countries other than my own'.

It should be clear that [2] is not meaningless under either interpretation. And it is also clearly not a tautology. Examples of actual tautological noun phrases (NPs) would be things like a red redness and a silent silence.

By the way, it is not clear to me that the corresponding examples that use the of construction, e.g. the silence of silence, are necessarily also tautological. Consider, for instance, the following quote:

The silence depressed me. It wasn't the silence of silence. It was my own silence. —Sylvia Plath, The Bell Jar, 1963 (link)

2. One needs to be careful when phrasing definitions

This one seems obvious, but it's easier said than done. OP's attempt at a definition was a decent one, but ultimately unsuccessful. Trouble could have been avoided if OP had used the relevant definition from the Oxford English Dictionary (OED), namely this one:

7. Situated outside the country; not in one's own land.

I will assume that postposing is an acceptable action. In that case, a foreign country becomes

[3] a country situated outside the country

This looks weird until we realize that there had to be some previous context, otherwise we would not know relative to where or whom the foreign country is in fact foreign. This context will make it clear that there is a certain country presently talked about, and so the country in [3] must be referring to that country. Thus, [4], restoring a bit of context, [3] becomes

[4] a country outside the country we are currently talking about

Not only is [4] a perfectly acceptable noun phrase in English, but also, in the context we are talking about, it is in fact equivalent to a foreign country.

3. A more general pitfall: in a sentence, one cannot always simply substitute a word by its literal dictionary definition and expect to obtain an equivalent sentence (or a sentence at all).

Sometimes one can, but sometimes not. As an example of when we cannot, take the sentence

[5] Four is an even number.

If we look at the relevant dictionary definition of the word even, we find

being any of the integers (such as −2, 0, and +2) that are divisible by two without leaving a remainder

But we cannot, in just any sentence where even appears in the relevant sense, simply blindly replace the word even by that definition. For example, if we try to do that with [5], we get

[6] ^*Four is a being any of the integers (such as −2, 0, and +2) that are divisible by two without leaving a remainder number.

which is not acceptable English (a fact marked by the asterisk in front).

Notice that postposing doesn't help, because the following isn't acceptable English, either:

[7] ^*Four is a number being any of the integers (such as −2, 0, and +2) that are divisible by two without leaving a remainder.

Originally posted answer

The term foreign country can have a range of meanings, but I will start with the more 'legalistic' one, because, given how you phrased the question, I think that is the one you are most interested in.

Foreign country vs another country

In the 'legalistic' sense, an equivalent question is whether it is possible for a citizen (or official institutions and laws) of a country A to regard a country B as another country (or a different country), but not as a foreign country. In other words, the question is whether the terms another country and foreign country can ever have different extensions.

And it seems that, at least sometimes, they can. An example would be the constituent countries of the United Kingdom. These traditionally include England, Scotland, and Wales, but in reality also Northern Ireland (see e.g. here for an overview and references).

The Oxford English Dictionary (OED), for example, lists this meaning (among others) for the adjective foreign:

7. Situated outside the country; not in one's own land.
In this and the following senses, the word is in British use not applied to parts of the United Kingdom, nor, ordinarily, to (former) colonies chiefly inhabited by English-speaking people. In the U.S. the designations of foreign corporation, foreign port, are sometimes applied to those belonging to other States of the Union.

So from the perspective of someone from England, Scotland may well be considered another country, but it's not a foreign country. If Scottland ever becomes independent from the UK, to a person from England, it would become a foreign country in this 'legalistic' sense. (Although, in a slightly weaker 'legalistic' meaning, perhaps it still wouldn't become truly foreign. As the OED says, it may be the case that from the perspective of someone from the UK, even countries such as Canada aren't foreign in this 'legalistic' sense.)

The UK (and perhaps The Commonwealth of Nations more generally) is not the only context where one can find examples of countries that, to each other, are other but not foreign. There are other groupings of countries that are similar to the UK in that they are a sovereign entity consisting of parts that are considered separate countries. For example, according to The Charter for the Kingdom of the Netherlands, that kingdom is made up from four countries: the Netherlands, Aruba, Curaçao and St Maarten. Within the Kingdom of Denmark, Greenland and the Faroe Islands are often referred to as countries, e.g. here.

If we consider historical entities, examples proliferate. For instance, many constituents of the Austro-Hungarian Empire could be fairly considered separate countries that weren't foreign to each other in the 'legalistic' sense: the Kingdom of Hungary and the Austrian Empire to start with, but also other entities, e.g. the Kingdom of Croatia-Slavonia within the Kingdom of Hungary.

'A foreigner in my own country'

There is, of course, a less legalistic way to think of the term foreign country. In some contexts, it could simply mean a country whose culture, society, laws, and customs are either unfamiliar or very different from those one is used to. In this meaning, it is even possible for one's own native country to be foreign to one. For an example of someone feeling this way, see this blog entry: 'When you're a foreigner in your own country'.

The relevant listing from the OED is 8.b.:

8.
a. Pertaining to, characteristic of, or derived from another country or nation; not domestic or native.

b. transferred. Unfamiliar, strange

On the flip side, suppose a citizen of a sovereign country A knows very well a sovereign country B. Then in the 'legalistic' sense, B is a foreign country to that citizen, but in the 'non-legalistic' sense we are discussing now, it is not.