Qualche/ Alcuno-- I'm still learning
I never get thrown by sentences that require you to use a singular noun after the word "qualche" any more.
Like the rest of you, I learned the hard way. I finally got sick of being marked incorrect, and I memorized the darned rule.
- Qualche mela = some apples
- Qualche libro = some books
That is until today, when I was doing a refresher on Present Verbs 1 and was told to translate, "Some fish fly".
"Aha!" I thought. "Can't fool me!"
And so I typed in:
- Qualche pesce volano
And it was marked incorrect!
The correct answer is apparently "Qualche pesce vola", if you were wondering. Even though "some" clearly points to plural, in English, in this case, which is why I chose "volano".
Do I now have to remember to use a singular form of a verb after qualche, as well?
Or is this only for "fish"? Or only when qualche is an adjective (I think it can become an adverb, too....)
I've encountered the same confusion with another adjective: Alcun (alcuna/ alcuno/ alcun'/ alcune/ alcuni) and I've decided that, unlike qualche, they don't require a singular noun to follow if they are already plural:
- Alcune mele
- Alcuni uomini
But "alcun", "alcuno" and "alcuna" are by nature singular (and I'm never truly sure when to chose alcun over alcuno anyway), so are phrases like "Alcun libro" and "Alcuni libri" interchangeable?
I know that in the "negative" you can say: "Non c'è alcuna fretta" ("There is not any hurry.")
But I can't think of an example in the "positive" sense.
"Do I now have to remember to use a singular form of a verb after qualche, as well? Or is this only for "fish?"
Yes, if the noun is singular (even if only because you are using qualche) then it must always be treated as such.
"and I'm never truly sure when to chose alcun over alcuno anyway"
Use the same rules as for un/uno.
- Alcuno scrittore
- Alcun messaggio
"are phrases like "Alcun libro" and "Alcuni libri" interchangeable?"
No, alcun/alcuno/alcuna (singular) mean any, whereas alcune/alcuni (plural) mean some.
Alcun libro = any book
alcuni libri = some books
As PietroFormano wrote, alcuno is not just the singular form of alcuni.
Alcuni is a common indefinite adjective or indefinite pronoun for "some" + plural noun (obviously, a countable noun), which can be colloquially replaced by the more informal un po' di + plural noun, or by qualche + singular noun:
Alcuni giornali. = Some newspapers.
Un po' di giornali. = A few/Some newspapers. [informal]
Qualche giornale. = (same)
Instead, alcuno is only used in negative sentences, as a replacement for nessuno acting as an adjective (→ "no/any" + noun), in order to avoid a double negative construction, thus sounding slightly more stylish, or more refined.
Remember that nessuno used as a pronoun can refer only to people ("nobody/anybody"), while used as an adjective it can refer both to people and to inanimate nouns ("no/any" + noun):
Non ho visto nessuno. = I haven't seen anybody. [double negative, only construction]
Non ho visto alcuno. [← very odd/unusual! ]
Non ho visto nessuna persona. = I haven't seen any person. [double negative]
Non ho visto alcuna persona. = I haven't seen any person. [slightly more stylish/literary]
Non ho visto nessun negozio. = I haven't seen any shop. [double negative]
Non ho visto alcun negozio. = I haven't seen any shop. [slightly more stylish/literary]
Instead, when the verb is not negative (no non before the verb), alcuno can never replace nessuno:
Nessuno può fare questo. = Nobody can do this.
Alcuno può fare questo. [←wrong ]
Nessuna persona può fare questo. = No person can do this.
Alcuna persona può fare questo. [←wrong ]
In some emphatic contructions alcuno can stand after the noun:
Non c'è alcun dubbio. = There is no doubt.
Non c'è dubbio alcuno. = There is no doubt. [slightly more emphatic, or literary]
Instead, alcuno can replace nessuno as a pronoun (i.e. without a noun, referring to people) if it is followed by a relative clause, or by a specification ("not ... any of...", rephrased as "none of..."):
Non c'è nessuno che sappia guidare l'automobile. = There isn't anybody who can drive a car. [double negative]
Non c'è alcuno che sappia guidare l'automobile. = (same) [stylish / literary]
Non c'è nessuno dei tuoi amici. = None of your friends is there (literally, "There isn't any of your friends") [double negative]
Non c'è alcuno dei tuoi amici. = (same) [stylish / literary]
But this use is very rarely heard in the spoken language, being now mostly literary.