What are Assemblage and Collage? What are the similarities and differences?

These two
terms, applied to works of visual art that eschew traditional paint-on-canvas techniques, are
related in their attention to physical objects arranged in visual, even symbolic, patterns and
shapes.  Art is looking at things carefully, according to Saroyan, and these forms of art make
the viewer look with fresh eyes at patterns, shapes, shadows, etc.   Differing from pure
sculpture in that they are still meant to be viewed from a face-front position, albeit having
some three-dimensional form, they are both visual collections; the main difference between the
terms is in the sameness or differences of the assembled objectsa collage (from French
coller-glue), probably coined by Picasso, uses similar patches of material or colorful
two-dimensional shapesphotos, for example, or swatches of cloth or paper, and either repeat
patterns or build a pattern of their own; an assemblage on the other hand, uses
three-dimensional objects, often found objects, either alike in theme or shape, or purposely
varied, to create a new arrangement of familiar materials.  Joseph Cornell is perhaps the
assemblage artist with the strongest reputation for the form; earlier artists of the 20th
centuryPicasso, Dubuffet, Duchamp, etc. did not separate these two terms with any
regularityDubuffet, for example, referred to his collection of butterfly wings as a collage,
but named the piece assemblage demprientes.  The other complication is that these artists
sometimes combined traditional oil painting on canvas with objects attached, calling these
pieces assemblages (the most famous of these might be href="https://en.wikipedia.org/wiki/Robert_Rauschenberg" title="Robert
Rauschenberg">Robert Rauschenbergs Canyon( 1959), officially described in
the National Gallery of Art as Assemblage: oil, housepaint, pencil, paper, fabric, metal,
buttons, nails, cardboard, printed paper, photographs, wood, paint tubes, mirror string, pillow
& bald eagle on canvas.  So the difference between the terms, both of which are used rather
loosely, might be stated as collages are pieces of flat material, glued into basically
two-dimensional patterns, and framed like an oil painting while assemblages are a gathering of
small three-dimensional objects, either found or collected into patterns with new relationships
among them.  As is the case with many post-facto art terms, they are not perfectly descriptive,
nor are they used with much differentiation or discrimination by historians and
scholars.