The answer.
Piamun: Although many people indifferently speak of monasteries instead of Cœnobia, yet there is this difference, that monastery is the title of the dwelling, and means nothing more than the place, i.e., the habitation of monks, while Cœnobium describes the character of the life and its system: and monastery may mean the dwelling of a single monk, while a Cœnobium cannot be spoken of except where dwells a united community of a large number of men living together. They are however termed monasteries in which groups of Sarabaites live.
Source: Conferences (New Advent)