Museum, library, gallery, archives, treasury are comparable but not synonymous terms when they mean a place serving as a repository for monuments (see DOCUMENT 1 for this sense) of the past.
Museum is the most general of these terms; it usually implies the intention both to preserve and to exhibit for the education of the public. A museum may be an institution concerned with the preservation and exhibition of objects of historical or scientific interest, especially such as illustrate the development of human civilization or the evolution of species, or it may be one providing for the preservation and exhibition of works of fine art (as paintings and sculptures), or it may combine both purposes. Consequently, the term is usually qualified in proper names or in general designation.
Library is applicable to a place (as a room, building, or institution) which houses a collection of books not for sale but available for use by specified persons or sometimes the general public.
But library is applicable also to a collection of literary material and as such may vary in scope from a handful of books making up a personal collection to a usually public collection consisting of a vast store of books of all kinds and of all ages, manuscripts, records, documents, files of journals, and often, in addition, works of art and serving primarily to preserve works of literature and of reference and documents in all fields of research and to make them available to scholars.
Gallery (often art gallery ) is used for a room, a suite, or a building housing and exhibiting works of art and especially paintings and pieces of sculpture. The term is used of a place housing a private as well as a public collection and (especially in the plural, galleries ) of a place where works of art are exhibited for sale.
Archives, when the term designates the place where a collection of old records, old documents, old files, and similar papers are kept rather than the collection itself (see DOCUMENT 1 ), may refer to a building or, as is more common, to a part of a building (as of a library or museum) where such a collection is housed.
Treasury is used to designate a place, often a room, where possessions of intrinsic value and often historical significance are stored and in some instances displayed to visitors. The term is often extended to things or places that are or are felt to be storehouses of precious things.