Human animate plural - двое, трое,

Question

This answer gives a short idea of using human animate plural forms, e. g. that they are used for persons only (?!). However, it's not quite clear, when they apply.

For instance:

за стеной стоят пятеро женщин и трое мужчин.
за стеной стоят пять женщин и три мужчины.

придут двое бизнесменов на встречу.
придут два бизнесмена на встречу.

Questions

• Are these sentences grammatically and semantically correct?
• What's the difference in meaning between using a number and the animate plural?
• When can the animate plural be used? Is it always when it designates an animate being?

Answer 1

These are called collective plurals ("собирательные числительные").

1. Usually it is considered that "collective" plurals двое, трое, четверо and so on are used only for nouns of masculine and common gender. "пятеро женщин" is incorrect, though natives sometimes make such mistake (as it is not clear why you should not do so: probably, etymologically it was not used for feminine). These numerals are normally used with nouns denoting people, those or masuline and common gender. Also used with люди, ребята, дети, лица.

2. The difference is that it is a "collective" plural, so it more closely views people as a single group. A shade of meaning, I'd say. The difference in use is that, first, you rarely go beyond "семеро" and, second, oblique cases of collective plurals are really rare. So while you may see something like "С теми двоими мужчинами что-то не так" ("Something's wrong with these two men") once in a while, it is by no means a natural construction, and you would sound non-native should you use it often (fortunately, it look so convoluted that you are unlikely to use it often :))

3. The one additional use you should remember is for pluralia tantum nouns: those that are used only in plural (like English "scissors", "pants"): штаны, ворота, ножницы, сутки, часы. Remember, in Russian when you need a Nominative-like form of number+noun for 1,2,3,4, you need Nom/Gen singular? But those nouns do not have singular! So instead you use:

   • одни ножницы
   • двое/трое/четверо ножниц, also пятеро, шестеро ножниц. Some sources say that "двое/трое/четверо" should not be used with such nouns, some say nothing like that. And use normal numerals in oblique cases. It becomes convoluted with numbers like 22,23,54 and so on. Believe it or not, they just cannot be used with such nouns. Though you may always say something like "22 items of scissors" (22 штуки ножниц) or just "more that twenty scissors", which is more useful anyway. The whole problem probably originated in the fact that people do not often use large numbers in colloquial speech.

Answer 2

According to many dictionaries this form can be applied to animate nouns that have masculine or common gender or to plural personal pronouns. Here's an article from Малый академический словарь (articles for other numbers are almost the same):

трое
трои́х, числ. собир.
Три (счетного значения не имеет, употребляется с существительными мужского или общего рода, обозначающими лиц, а также с существительными, имеющими только мн. ч., и с личными местоимениями во мн. ч.).
Три девушки и трое юношей. Трое суток. Вам троим. У них троих.

As you can see - the first example shows that you cannot say трое девушек (or пятеро женщин): only три девушки, пять женщин.

Трое суток is (I believe) an example of common gender noun. Other dictionaries call this example "существительные не имеющие формы единственного числа" (nouns that do not have singular form). Other examples of such nouns are очки, часы, штаны, брюки, etc.

Вам троим. У них троих. is an example of usage the words двое, трое, etc. with personal pronouns.

1. Are these sentences grammatically and semantically correct?
   As you can see, the пятеро женщин is not correct. As far as I know there is no big difference between три мужчины and трое мужчин. On the other hand you cannot say три суток, only трое суток is allowed. Same for "нас три" is not correct - only "нас трое" is correct.
2. What's the difference in meaning between using a number and the animate plural? There is no difference in meaning.
3. When can the animate plural be used? Is it always when it designates an animate being? No, it doesn't always mean the animate. Ножницы and сутки are not animate.