I. doc ‧ u ‧ men ‧ ta ‧ ry 1 /ˌdɒkjəˈmentəri◂, ˌdɒkjʊˈmentəri◂ $ ˌdɑːk-/ BrE AmE noun ( plural documentaries ) [countable]
a film or a television or radio programme that gives detailed information about a particular subject
documentary on/about
A local film crew is making a documentary about volcanoes.
II. documentary 2 BrE AmE adjective [only before noun]
[ Word Family: noun : ↑ document , ↑ documentation ; verb : ↑ document ; adjective : ↑ documentary ]
1 . documentary films, programmes, photographs etc give or show information about a particular subject:
documentary films
2 . consisting of or written on documents
documentary evidence/proof
One of the most useful sources of documentary evidence is maps.