It's time to explore few strange nouns: they have a bit strange case forms, some of them lack plural or singular forms, and — the strangest thing — some cannot be counted with normal ordinal numbers (pet, šest...)!
This chapter is a bit complex, but I think you should know how to count children! Therefore, I cannot omit it...
There are some n-nouns that are not irregular, but really form a set of small sub-classes within n-nouns. Some common nouns are among them. A prototype of such nouns is ime n "name".
In nom.sg. and all cases without endings (well, just acc.sg.) it has this form, but in other cases, -en- is inserted before regular ending. For some other nouns, -et- is inserted; for some -ev; for a really small group, -es- is inserted, but in plural only, and it's optional for them. The patterns are:
nom.sg. im-e už-e podn-e čud-o acc.sg. dat.sg. im-en-u už-et-u podn-ev-u čud-u gen.sg./dual im-en-a už-et-a podn-ev-a čud-a ins.sg. im-en-om už-et-om podn-ev-om čud-om nom.pl. im-en-a už-et-a podn-ev-a čud-es-a / čud-a acc.pl. dat./ins.pl. im-en-ima už-et-ima podn-ev-ima čud-es-ima / čud-ima gen.pl. im-en-a už-et-a podn-ev-a čud-es-a / čud-a
Here is a list of frequent nouns that insert -en-. There are not too many of them:
sljëme "ridge" (of roof, mountain)
prezime "family name"
vrijëme "time", "weather"
The noun vrijëme means both "time" and "weather". Its forms in other cases are vrëmenu, vrëmena, etc. For example, this is a very frequently used question:
Imaš (li) vrëmena? "Do you have any time?"
The genitive is used instead of acc. as "partitive" implying "some amount of". In the next example noun is used in the other meaning (recall that kakäv means "what like" and changes as an adjective):
Kakvo je vrijëme? "What is the weather like?"
Only five nouns insert -ev-:
prijëpodne "before noon"
dopodne "before noon"
There are only three nouns that insert -es-, but they have also forms without -es-; when extended, they shift meaning a bit, and stand for "big bodies", "great wonders", "wide skies":
čudo "miracle" nebo "sky" tijëlo "body"
The following often used nouns insert -et-:
lane "baby deer"
jare "baby goat"
Noun drvo means "wood" as a material, but also a single "tree". When it means a tree, it also has an -et- inserted: nom. drvo, dat. drvetu, nom.pl. drveta, etc.
Many nouns with -et- have similar meanings: they are young ones, of people, other animals, or "egg". Jaje "egg" has also more usual forms jaju, jaja, etc.
But the weirdest aspect is that such nouns for young animals (except jaje when not inserting -et-) have no regular plural — another noun must be used instead, a so-called collective noun (abbreviation: coll.). All collective nouns are oddballs, either they don't have singular or don't have plural.
All the above listed -et- nouns — except for dijëte and drvo — use collective nouns on -ad (janjad, telad, jarad, lanad, užad...). They are i-nouns in singular and of course, they have f gender; they exist only in the singular, and are uncountable (but their meaning is multitude, plurality).
Telad je u štali. "Calves are in (the) barn." (lit. "is...")
Tele je u štali. "(The) calf is in (the) barn."
Recall that there are also diminutives, words for small things. For some animals, they are preferred to the words above for young animals. For instance mačić "small, baby cat" is preferred in most of Croatia, while mače "kitten" is preferred in Bosnia and Serbia. The same goes for pačić (more frequent in Croatia) vs. pače (common elsewhere). There's also a word pilić meaning "small chick" which is used often instead of pile. You see, Croatian has a rather large vocabulary...
The Strangest Noun: dijëte
However, dijëte "child" uses as its plural form a collective noun djëca, a noun that behaves as a regular a-noun having singular only. The complicated part is that it demands adjectives for f.sg., but when verbs come into play, it behaves as if it were in the plural:
Moja djëca su došla. "My children came." (moja = nom.sg.f but su = pl.!)
Razgovaram s mojom djëcom. "I'm talking to my children." (mojom = ins.sg.f!)
I call the behavior of djëca the mixed gender, and it's the last and smallest (by number) gender in Croatian (and of course the weirdest — so I called it the "x" gender).
Another noun behaving like this is a collective braća "brethren". Yet another one is gospoda "gentlemen" (from gospodin ma "gentleman"). There are few other nouns in this group that will be introduced immediately.
Nouns in the mixed gender get their case endings as a-nouns in singular, agree with adjectives for feminine singular, but demand plural verbs.
Examples are braća "brethren", gospoda "gentlemen", and djëca "children". The corresponding nouns brat ma "brother", gospodin ma "gentleman", and dijëte n "child" have forms for singular only.
Another weird feature of djëca, braća and similar nouns is how they use numbers. They use a special construct, involving collective numbers.
There are two types of nouns that are generally derived from numbers. The first one have the same form in all cases, and are used to stand for people of mixed or unknown gender. The second one means "x men", and stands for groups of all-male persons only.
# "n people" "n men" 2 dvoje dvojica 1+1 oboje obojica 3 troje trojica 4 četvero četvorica 5 petero petorica 6 šestero šestorica ... ...
The nouns in the first column are actually permanently in acc. pl. and have n gender; you will hear:
Nas dvoje je došlo. "We two came."
Besides these forms, forms with -oro are used sometimes: četvoro, šestoro, etc. Neither of them change forms in various cases.
The nouns in the second column mean "so many men, all of them male". These nouns behave as nouns braća and djëca — they belong to the mixed collective gender and have forms like a-nouns in the singular:
Vidio sam ovu dvojicu. "I have seen these two (men)." (ovu = acc.sg.f)
Dvojica su došla. (su = pl.)
Note that these nouns do change case, unlike the nouns of the first type. We can call these nouns "people-collective" and "men-collective" (I have invented those names!)
Now we finally get the answer how to count children! We use collective nouns of the first (people) type! Therefore, counting will have (as you likely expect) form noun + noun-in-genitive, but for the noun djëca we must use people-collective numbers:
Imamo dvoje djëce. "We have two children."
Šestero djëce je došlo. (došlo = sg. n !) "Six children came."
The same applies to braća "brethren":
Imam dvoje braće. "I have two brothers."
Imao je sedmero braće. "He had seven brothers."
Of course, for 2-4 children and brothers you can use singular nouns in the dual form, e.g.:
Imam dva brata. "I have two brothers."
Imamo tri djeteta. "We have three children."
But you cannot use them for 5 and more — you must use plural nouns, and these two nouns demand people-collective numbers.
For numbers 2-4 you can use both options; however, you will notice that people slightly prefer dva brata to dvoje braće, and for "child" exactly the opposite, dvoje djëce is more common than dva djëteta!
Sometimes people use people-collective nouns even for groups of men (e.g. dvoje for 2 men). That's considered colloquial, not Standard, but it can be heard often.
You can use collective nouns to count other nouns as well; it's common to use people-collective nouns with the noun ljudi "people" (e.g. troje ljudi) and men-collective ones with nouns for men in plural (e.g. petero radnika).
I'm sure you've never dreamed that such complications exist. I'm really sorry.
n-Nouns Without Singular and With Double Plural
Some n-nouns have only plural; the common ones are:
kola "cart, coach"
jetra "liver" (lit. "livers")
pluća "lung" (lit. "lungs")
vrata "door, gate" (lit. "gates")
They look as if they are feminine, but really it's neuter plural! They are used in plural even when you mean just one item, similar to English "trousers":
Moja usta su zatvorena. "My mouth is closed."
Iza velikih vrata. "Behind the big door."
Two n-nouns have two types of plural: one regular, and another as i-nouns in plural; in the second plural the gender is changed accordingly to the feminine. They are oko "eye", and uho "ear". Their second plurals are oči and uši as i-nouns in plural, but with an optional -ju in gen.pl:
nom.pl. oči uši acc.pl. dat./ins.pl. očima ušima gen.pl. oči, očiju uši, ušiju
Regarding the agreement with adjectives and verbs, they behave as expected: i-nouns are feminine nouns:Tvoje oko je plavo. "Your eye is blue." (tvoje, plavo = nom.sg.n)
Tvoja oka su plava. "Your eyes are blue." (tvoja, plava = nom.pl.n)
Tvoje oči su plave. "Your eyes are blue." (tvoje, plave = nom.pl.f — this is normally used)
Forms oka and uha are used only in poetry, when talking with in a very emotional context, and metaphorically, when e.g. about "eyes" of a fishing net, for example.
Nouns mati and kći
Noun kći "daughter" has peculiar forms: all except nom.sg. are made from kćer-. A similar noun is mati; both are odd i-nouns:
nom.sg. kći mati acc.sg. kćer mater dat.sg. kćeri materi gen.sg. matere (!) ins.sg. materi nom.pl. kćeri matere (!) acc.pl. dat./ins.pl. kćerima materima gen.pl. kćeri matera (!)
Many people use kćer as nom.sg., to horror of the language police. Also, it's a frequently used as a trick-question in quiz shows, etc. However, there's another word — kćerka, a regular a-noun of the same meaning, and much easier to use. You can use either one.
The word mati is not often used nowadays; majka, a perfectly regular a-noun, is more often used instead.
Common Collective Nouns
Furthermore, there are some n-nouns that are collectives of other nouns. They behave just as any other n-nouns, but don't have plural. They are used in meaning "all such things", "a bunch of such things", etc., and are really often used. Once again, they are just plain n-nouns, having n gender, but have singular only and take verbs in singular. Here is a list of often used ones with corresponding nouns for a single object (all single-thing nouns have a plural, but I listed only for m-nouns, to show if they insert -œv-):
cvijëće coll. "flowers" ← cvijët mi "flower" pl. cvjëtovi
drveće coll. "trees" ← drvo n "tree, wood"
granje coll. "branches" ← grana f "branch"
grmlje coll. "bushes" ← grm mi "bush" pl. grmovi
grožđe coll. "grapes" ← grozd mi "cluster, grape" pl. grozdovi
kamenje coll. "rocks" ← kamen mi "rock, stone" pl. kameni
lišće coll. "leaves" ← list mi "leaf" pl. listovi
smeće coll. "trash" (no single noun exist)
trnje coll. "thorns" ← trn mi "thorn" pl. trnovi
As you can see, the -'je suffix is added after the nominative ending is discarded, causing j-softening!
I must say again, collective is not a special gender, it's just some nouns with a special meaning. They are really often used, so many people never use cvjëtovi "flowers", but only the collective. However, when counting, you must use the single-thing nouns, since collectives are uncountable (like English "salt", "flour"):
Dobila sam jedan cvijët. "I got one flower." (cvijët = acc.sg.; female speaker)
Dobila sam dva cvijëta. "I got two flowers." (cvijëta = dual = gen.sg.)
Dobila sam četiri cvijëta. "I got four flowers." (cvijëta = dual = gen.sg.)
Dobila sam pet cvjëtova. "I got five flowers." (cvjëtova = gen.pl.)
Dobila sam cvijëće. "I got flowers." (cvijëće = acc.sg., uncountable!)
People most often use the last sentence, meaning they got "some number of flowers". So collectives are really often used, who is going to count all the trees, rocks and thorns...