I think it's not
that difficult as it may seem. It sure is
quite complicated, but it shouldn't take more than two afternoons to master it. There are two main divisions.
I. Countable nouns may be:
1) singularia tantum with the plural meaning (e.g. deca, braća, telad)
- they combine with
collective numbers (and in some cases also with numeral nouns)
2-4: dvoje dece, troje braće, četvoro teladi
(also dvojica, trojica, četvorica braće)
The forms dva deteta, tri brata, četiri teleta (from dete, brat, tele) are interchangeable with the forms dvoje dece, troje braće, četvoro teladi (from deca, braća, telad).
5+: petoro dece, petoro braće, petoro teladi
(also petorica braće)
The forms dvoje, troje, četvoro, petoro braće and dvojica, trojica, četvorica, petorica braće are interchangeable.
2) pluralia tantum (e.g. nogari, kočije, vrata)
- they combine with
numeral adjectives (and in some cases also with cardinal and collective numbers)
1: jedni nogari, jedne kočije, jedna vrata
2-4: dvoji nogari, troje kočije, četvora vrata
(also dvoje, troje, četvoro vrata, see
above)
5+: petori nogari, petore kočije, petora vrata
(also pet vrata and petoro vrata, see
above)
The forms such as pet vrata and dvoje, troje, četvoro, petoro vrata are widely used in speech, but they are not accepted by the norm.
3) all other countable nouns (e.g. muškarac, računar, žena)
- they combine with
cardinal numbers (and in some cases also with collective numbers and numeral nouns)
2-4: dva muškarca, tri računara, četiri žene
(also dvoje and dvojica muškaraca)
The forms dva muškarca, dvoje muškaraca, dvojica muškaraca are interchangeable. They can be distinctive only with those masculine nouns that are not specified for sex: dva studenta means two students whose sex is not known and not important, dvoje studenata - two students of both sexes, dvojica studenata - two male students. But this distinction is on its way to be lost and is not strictly maintained in speech (except for the last option dvojica studenata, which always denote two male students). Thus dvoje studenata may be used instead in the meaning of dva studenta, so to enforce political correctness, or instead of dvojica studenata, even if both students are male.
5+: pet muškaraca, pet računara, pet žena
(also petoro and petorica muškaraca)
The nouns brat, from the first declension (dva, tri, četiri brata), and dete, from the second declension (dva, tri, četiri deteta), don't have regular plural forms. The singularia tantum nouns braća and deca are used instead (petoro braće, petoro dece). Other nouns from the second declension, such as drvo (dva, tri, četiri dȑveta), do have regular plural forms, but these forms (pet drvèta) for some reason sound odd in most cases.
The masculine nouns from the third declension such as tata and deda should be used only in combination with numeral nouns: dvojica tâta, dvojica dêda. Those such as violinista may be used with collective numerals: dvoje violinista, meaning two violinists of either sex, or numeral nouns: dvojica violinista, meaning two male violinists. For numbers five and above cardinal numbers may be used too: pet violinista, petoro violinista, petorica violinista. Pet violinista would denote five violinists whose sex is not known and not important, petoro violinista - five violinists of both sexes, petorica violinista - five male violinists. But, same as above, this distinction is not strictly maintained in speech.
That should be more than enough of what there is to know so that you can use the right numeral construction with every noun.
II. Numeral constructions may be:
1) paucal phrases with cardinal numbers 2-4
- only nouns that have both singular and plural
- the number acts as an attribute, the noun is in its
(nominative) paucal form
- declinability: limited
- congruence: with the noun, as it is the head of the phrase
2) partitive phrases
2a) with cardinal numbers 5 and above
- only nouns that have both singular and plural (in everyday language also neuter pluralia tantum)
- the number acts as the head of the phrase, the noun is in its
genitive plural form
- declinability: no
- congruence: grammatical or semantic, see
above
2b) with collective numbers (dvoje, troje, četvoro, petoro...)
- singularia tantum with the plural meaning and masculine nouns with the feature [+human] to denote a group of people whose sex is not known and not important (in everyday language also neuter pluralia tantum)
- the number acts as the head of the phrase, the noun is in its
genitive plural form
- declinability: limited for 2-4, no for 5 and above
- congruence: grammatical or semantic, see
above
2c) with numeral nouns (dvojica, trojica, četvorica, petorica...)
- only masculine nouns with the feature [+human] to specifically denote a group of males
- the numeral noun acts as the head of the phrase, the noun is in its
genitive plural form
- declinability: full
- congruence: grammatical or semantic, see
above
3) phrases with numeral adjectives (dvoji, troji, četvori, petori...)
- numeral adjectives combine only with pluralia tantum
- the numeral adjective acts as any other adjective, the noun may be in
any of its (plural) forms
- declinability: full
- congruence: with the noun, as it is the head of the phrase
That should be
all there is to know on this subject, but I'm not sure anymore about it being
quite complicated, still not
that difficult. Anyway, I'll really stop posting now.
