This is the 2725th most frequent French word.
australien
Australian (relating to Australia or its inhabitants).
In this sentence, 'australien' is used as an adjective modifying the noun 'étudiant', specifying the nationality of the student.
L'étudiant australien étudie la biologie marine.
The Australian student is studying marine biology.
Here, 'australiens' acts as an adjective describing the noun 'documentaires', indicating the origin of the content.
Il aime regarder des documentaires australiens.
He enjoys watching Australian documentaries.
In this example, 'Australien' is used as a noun referring to an individual of Australian nationality or origin.