-arium

A place or container connected with, or employed for, some purpose.

Latin, the neuter ending of adjectives in ‑arius.

The first terms in English were for places connected with Roman life, as in caldarium, tepidarium, and frigidarium, respectively the hot, intermediate, and cold rooms of Roman baths.

Several words indicate places containing collections: aquarium, a tank for keeping water creatures or a building containing many of them; herbarium (Latin herba, grass, herb), a collection of dried plants; and terrarium, a place in which smaller land animals are kept; the general term for a place in which to keep living things is vivarium (Latin vivere, to live). More recent examples, such as dolphinarium and oceanarium, as much suggest a place of public entertainment as one where animals are housed; a planetarium is a domed building in which images of the sky are projected for entertainment or education.

Other examples are honorarium, a payment given for professional services that are rendered nominally without charge, and armamentarium (Latin armamentarium, an arsenal) at first the medicines, equipment, and techniques available to a medical practitioner, now more generally a collection of resources available for a given purpose.