двоје / троје / четворо

Collective numerals (збирни бројеви: двоје, троје, четворо, петоро...; note that standard Serbian normatively prefers endings in -оро like четворо and петоро, though doublets in -еро such as четверо and петеро are also recognized standard variants, especially common in Ijekavian standard usage) quantify groups viewed as a single collective set.

1. Primary Uses:

• Mixed-gender groups of people: When quantifying mixed-gender groups using a single count noun, collective numerals are the standard, normative choice (e.g., двоје студената = two students [mixed-gender group]; троје колега = three colleagues [mixed group]). Unlike feminine or masculine cardinal numerals—where два студента refers exclusively to male students and две студенткиње strictly to female students—collective numerals neutralize gender distinction to represent heterogeneous groups. For groups of 5 and above, either collective numerals (петоро студената) or standard generic cardinal numerals (пет студената) are routine and standard. Note that compound numerals ending in 1 (e.g., двадесет један студент) cannot form collective numerals at all.
• Exclusively female groups or male count nouns: Groups of all women take feminine cardinal numbers (две жене, три колегинице). To refer exclusively and unambiguously to male persons, Serbian often uses dedicated masculine personal numeral nouns (двојица мушкараца, тројица колега, петорица студената), alongside standard cardinal numerals (два човека, пет мушкараца).
• With collective nouns for young beings: Obligatory with collective nouns such as деца (двоје деце, троје деце; never *две деце) and collective stems for young animals like јагњад or пилад (троје јагњади, четворо пилади). Note that when counting children, speakers also regularly and standardly use cardinal numbers with the singular neuter count noun дете (два детета, три детета, четири детета).
• With collective masculine nouns (браћа, господа): When referring to male groups expressed by collective nouns, both collective numerals (троје браће, четворо господе, седморо браће) and numeral nouns in -ица (тројица браће, четворица господе) are fully normative, standard, and accepted.

2. Distinction: Collective Numerals vs Numeral Adjectives:
Do not confuse collective numerals (двоје, троје, четворо) with numeral adjectives (бројни придеви: двоји / двоје / двоја, троји / троје / троја, четвори / четворе / четвора). Numeral adjectives decline like adjectives and are used with plural-only nouns (pluralia tantum) as well as paired items or composite sets: двоја врата (two doors), троје маказе (three pairs of scissors), четворе панталоне (four pairs of trousers), двоје рукавице (two pairs of gloves), двоја одела (two suits).

3. Case Government:

• Standard countable nouns of persons take the genitive plural: четворо студената, петоро пријатеља.
• Collective nouns take their genitive singular form: двоје деце, троје јагњади.

4. Predicate Agreement:

• When the subject denotes human beings, the predicate in past tenses can take formal neuter singular agreement (Петоро студената је дошло) or semantic masculine plural agreement (Петоро студената су дошли). Semantic agreement is mandatory with personal pronouns: Нас двоје смо разговарали.
• When quantifying young animals, only grammatical neuter singular agreement is permitted: Троје јагњади је побегло (never *су побегли).

5. Declension:
Numerals from четворо onward are completely indeclinable (Разговарали смо са четворо колега). While older or bookish style features inflected oblique case forms for двоје and троје—specifically genitive (двога / двојега, трога / тројега) and dative/locative/instrumental in -ма (двома, трома)—these are archaic in contemporary standard Serbian. In modern daily usage, collective numerals are overwhelmingly treated as indeclinable (Пришао је њима двоје, Разговарао је са њих двоје).