"A murder of crows" (what's up with that?)
I've seen this kind of plurals (or groups names, I think), where the ussual noun (as in "a flock of crows") is changed for another word with its own meaning ("a murder" is an unlawful killing). All this sounds really snobbish to me. Is this something in use? Is it wrong to use the common noun?
3 Answers
I was going to answer but see Ian has, - yes murder is correct and ravens are an unkindness, geese are a gaggle [ or in flight a skein or wedge], but many native English speakers do not know all the many words we have for a group of particular animals or birds. Therefore 'flock' would be the wrong answer to a quiz question,but would be fine describing any group of birds. Flock is also used for a group of sheep but herd for a group of cattle. I haven't checked what the Spanish alternatives are - maybe right for a game!
Here's a list of almost all of them
Practically speaking, you won't need nearly this much in informal speech. Some are used a lot (for example "a herd of cattle") while other ("an army of frogs) aren't used outside of formal writing.
The ones you really have to know to communicate informally are (off the top of my head) "herd", "flock", "litter", "pack", "flight", "group", "pride", "swarm" and "school"
I'd recommend using this list as a reference and not memorize something on here until you've herd the expression in real life. Consult this often, but don't forcibly memorize it.
We have lots of these in English.
A murder of crows is correct.
Example:
A group of swans is called a bevy or a wedge when in flight