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Yesterday I came across the term радиус-вектор in physics, which surprised me because the order of the two parts is reversed by comparison with the terms вектор-строка and вектор-столбец in linear algebra, which I knew earlier. Does anyone have a suggestion for why it would be reasonable to use вектор as the second part of the term in one case but as the first part of the term in the other cases? For comparison, in English the terms are all built in the same way: radius vector, row vector, and column vector.

I don't know when these terms entered the language, but for instance if вектор-строка had been in use first then I'd think вектор-радиус would be a closer fit to the "established" format than радиус-вектор, and likewise for строка-вектор if радиус-вектор had been introduced first.

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  • Well, slightly off-topic comment: maybe because вектор-строка and вектор-столбец are well defined mathematical terms. I don't speak mathematical Russian, or not good enough, but when I studied physics I heard radius vector only the first two semesters. I'd avoid that terminology and say позиция instead, if such term exists in Russian: I think everybody would know that it's a vector, which usually depends on time if you do the dynamics, etc.
    – c.p.
    Dec 30 '13 at 8:48
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In compound nouns like

  • самолёт-истреби́тель
  • самолёт-разве́дчик
  • самолёт-невиди́мка
  • ве́ктор-строка́
  • ве́ктор-столбе́ц
  • спортсме́н-лы́жник
  • спортсме́н-плове́ц
  • садово́д-люби́тель

the first noun gives a more general description of the word and the second one gives a more specific description. First consider several other examples and then let us discuss words вектор-строка, вектор-столбец, and радиус-вектор. “Самолёт-невидимка” is an aircraft (this is a more general description) and more specifically it is a stealth aircraft (this is a more specific description); it would not make much sense to describe it as a stealth object (“невидимка”), which is more specifically a stealth aircraft. Similarly, “садовод-любитель” is a gardener, more specifically, an amateur gardener; again it would not make much sense to say that “садовод-любитель” is an amateur, more specifically, an amateur gardener.

Similarly, “вектор-строка” is a vector, specifically it is a vector written as a row; “вектор-столбец” is a vector written as a column. It would make much less sense to say that “вектор-строка” is a row that forms a vector (there is no separate mathematical notion of row).

Now “радиус-вектор” is the position (radius) of a point, which is written as a vector. The word вектор specifies that радиус-вектор gives not just the distance to the position but also the direction.

Perhaps one could argue that “радиус-вектор” should be called “вектор-радиус” because it is a vector that (more specifically) gives the position of an object. I think the main reason why “радиус-вектор” is used is the following. The term “радиус-вектор” is mostly used in physics not in linear algebra. The word вектор just specifies the type of the variable: \vec r is “радиус-вектор”, whereas r is радиус (скаляр/scalar). If “радиус-вектор” was a concept studied in linear algebra and we had different kinds of vectors, then we would have terms like: вектор-радиус, вектор-ускорение, вектор-функция.

Summary To check what word order to use, you can apply the following test. Write A-B if you can say “он/она — A, а точнее A-B”:

Это самолёт, а точнее самолёт-истребитель. not Это истребитель, а точнее самолёт-истребитель.

Пусть v — произвольный вектор, а точнее вектор-столбец. not Пусть v — произвольный столбец, а точнее вектор-столбец.

Пусть \vec r — радиус (положение) частицы, а точнее её радиус-вектор. not Пусть \vec r — вектор частицы, а точнее её радиус-вектор.

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    I see. That also explains for me the order of terms in other compound nouns like теоретик-числовик and пучок-небоскрёб, which are the reverse of the corresponding terms in English. It also explains why there is теоретик-числовик, теоретик-игорвик, and so on in math, but физик-теоретик rather than теоретик-физик: number theorists and game theorists are theorists who work on "numbers" (at least historically) and "games", while a theoretical physicist is more sensibly viewed as a physicist who works on theory rather than a theorist who works in physics. Thanks!
    – KCd
    Dec 30 '13 at 19:27
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An answer from a native speaker with a (somewhat rusty) math degree and no linguistic education.

If this is this радиус-вектор then the phrase emphasizes that this is a vector of some kind. "Vector" is the more important word here.

In the linear algebra terminology it is the difference between вектор-строка and вектор-столбец that is important. The differentiating word comes last, pushing "вектор" in front.

This is more of a heuristic than a rule cast in stone.

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Just as Vitaly Osipov said, the last word should be considered as main, while the first is subordinate. So your question can be reformulated: why ра́диус-ве́ктор is more vector than radius but ве́ктор-строка́ and ве́ктор-столбе́ц are more row / column than vector?

The answer, I guess, is quite simple. It’s in common visual representation. This is definitely a column for me:

enter image description here

This is defenitely a row:

enter image description here

And this is a vector:

rv

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Радиус-вектор is a vector, which is a radius, while for the single-row / single-column matrix it is the other way round. The primary concept is that of a row or a column, and being a vector is a secondary one.

Besides, I would assume that радиус-вектор is an old compound, which was directly copied from, say, German: http://de.wikipedia.org/wiki/Ortsvektor . This is true of so many scientific terms! English wasn't an influential language of science (and in general) in Russia until 20th century. That's why so many words familiar to the English speaker look strange or have queer stress in Russian.

"Вектор-строка" and "вектор-столбец" look to my eye like native-coined terms. We did not use them at all, mostly just referring to the rows and columns as "строка" as "столбец". In German they are Spaltenvektor and Zeilenvektor, so the words were definitely not borrowed as-is.

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  • What kinds of words did you have in mind with strange stress that otherwise look similar to English?
    – KCd
    Jan 13 '14 at 3:37
  • Actually, any word that looks like it could have been borrowed from English, but wasn't.
    – Shady_arc
    Jan 13 '14 at 10:33
  • Actually, many words that look like they could have been borrowed from English (with the same meaning of a somewhat different), but weren't: Интерес - interest, фамилия - family, университет - university, кафедральный - cathedral, эксцентриситет - eccentricity... I am sure many scientific words were borrowed from French or German in 19th century.
    – Shady_arc
    Jan 13 '14 at 10:40

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