Questions & Answers about В комнате сидели четверо.
Четверо is a collective numeral, while четыре is the ordinary cardinal numeral four.
Russian uses collective numerals like двое, трое, четверо mainly:
- with groups of people, especially when the group is thought of as a unit
- when the noun is omitted
- with children
- with some nouns that exist only in the plural
In this sentence, четверо works very naturally because it means something like four people / four of them.
Using четыре here by itself would sound incomplete to most learners, because четыре usually wants an explicit noun after it, such as четыре человека.
Yes, very likely.
Четверо can stand on its own and mean:
- four people
- four children
- the four of them
In В комнате сидели четверо, the noun is not stated because it is either obvious from context or simply not important. Russian often leaves it unstated when using collective numerals this way.
So the full idea is something like:
- В комнате сидели четверо человек
but in normal Russian, четверо alone is enough.