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Today we'll talk about the shift in word meaning which happens by someone's mistake, which, in turn, is being cloned by mass media. This article was inspired by news appeared today in multiple places.
The news was about Moscow's metro system. First, some brief information about it. Moscow metro's modern topology is quite straightforward: there is one circle line; the rest lines, which are more or less straight, cross that centrally located cycle.

There are also permanent plans to build up one or two new circle lines. The news I'm talking here is just about that.
So, let's go to news lines appeared on 21st February 2011.
Москва начинает строительство третьего радиуса метро Интерфакс 12:58 Столичные власти начинают строительство нового контура метро - от "Авиамоторной... NEWSru.com 15:25 В Москве началось строительство третьего радиуса метро Irn.ru 15:01 Станции метро избавят от перегрузок Дни.ру 14:56 Новому кольцу в метро дали зеленый свет Утро.ru 14:56 В столице начинается работа над третьим радиусом метро BFM.ru 14:28 Инициировано строительство третьего радиуса мосметро Взгляд.ру 14:09 В Москве начали строить новый радиус метро Lenta.ru 13:40 На "Планерной" развязали транспортный узел. В будущем в Москве построят еще 40 ... Известия 13:24 В Москве начинается строительство третьего радиуса метро REGNUM 13:22 От "Авиамоторной" начнут строить третий радиус московского метро GZT.RU 13:16 В Москве начали строить третий контур метро РБК 13:15 Работы по стройке III радиуса метро начинаются в Москве РИАН Недвижимость 12:47 Кузьмин: в Москве начинаются работы по созданию третьего радиуса метро РИА Новости 12:46 В метро начинают строить третий радиус - от станции "Авиамоторная" - главный ... ИТАР-ТАСС 12:45
As you may notice, most of these headlines say about opening of the third radius of Moscow's metro (третий радиус Московского метро).
Comparing that with a real map of Moscow's metro, you may notice that there are really more than three radiuses there. All the lines crossing the circle ones are called radial lines.
So, what was really meant by all those news?
Actually, it is not that easy to answer even for a native speaker. Having the news ordered by publishing time, it seems that the source of this confusion was based on the words of metro representative, whose quote is available in early articles:
«Мы начинаем строить новый третий радиус, от станции «Авиамоторная» в зону Кожухово, а дальше в зону Люберецких полей. Мы сегодня получили добро на первый участок третьего контура метрополитена, чтобы разгружать не только хвосты — дальние районы, но и снять нагрузку в центре», — сказал Кузьмин. (ИТАР-ТАСС)
«Мы начинаем строить новый, третий радиус, от станции «Авиамоторная» в зону Кожухово, а дальше в зону Люберецких полей. Мы сегодня получили добро на первый участок третьего контура метрополитена, чтобы разгружать не только хвосты — дальние районы, но и снять нагрузку в центре», — сказал Кузьмин. (РИА Новости)
Having two absolutely identical passages, we can assume that it is either exact quotation or copying from a third place. It has no practical meaning for us now.
News articles also mention that that new line is really a circled one, which makes everything clearer, as there are plans for building a second circle line, part of which is already operating for years.
Let's recap the words which may be used for describing metro lines:
кольцо — circle
радиус — radius
диаметр — diameter
хорда — chord
контур — contour
All of them are used for talking about Moscow's metro as well. What we see in today's news is occasional shift in meaning, when what is named by радиус really means кольцо.
Ad hoc explanation of that strange shift may be the following. Both радиус and контур are part of professional slang and suddenly appeared in the interview. I have no idea how that line is really called among metro people, but in public use it can only be кольцо or хорда. As it was said about the third radius, and there are already one full circle and the part of the second one, that may stand for the third circle line, or short: the third circle.
Thus, radius in this particular case means circle. Weird, incorrect, but used in multiple articles just in one day.
By the way, the meaning of radius itself is already shifted, as all the lines crossing the circle one are not really radiuses: they do not start in the centre, but rather cross it and go further. Diameter would be more correct word for that :-)
