dokumentaran

1. (of a film, programme) documentary
   Sinoć smo gledali dokumentarni film o Tesli. — Last night we watched a documentary film about Tesla.
   Volim dokumentarne serije o prirodi. — I love nature documentary series.
2. documentary; based on documents
   Muzej je otvorio dokumentarnu izložbu o Prvom svetskom ratu. — The museum opened a documentary exhibition about the First World War.

Usually used in the long form (dokumentarni film); colloquially a documentary film is often called dokumentarac.