The term MEDIUM can be applied to both the type of art in question (i.e. painting, pottery, photography) as well as the MATERIALS that go into making a work of art.
So, a sculpture can be produced in the medium of marble or stainless steel. A painting can be in the medium of oil paint or watercolors. An architect can build a building using the media of steel, glass or poured concrete.
Art Term: Medium, Tate Museum, London, UK, 2018. https://www.tate.org.uk/art/art-terms/m/medium
Julie Frith. "Mobuis: Modern Hanging Mobile Art Sculpture." (2010). ARTSTOR.
Cast concrete and steel construction.
Eero Saarinen & Associates (1962). "TWA Terminal (Trans World Airlines Terminal) Interior, Gallery Bridge." ARTSTOR
Art can be produced using many different materials.
The term MIXED MEDIA is used to describe works created from more than one type of material.
Alessandro Mendini. "Kandissi Sofa (Canapé Kandissi)" 1979. Materials: wood, leather, textiles. ARTSTOR
TECHNIQUE can be described as the personal way that an artist uses a medium. Painters Chuck Close and Georges Seurat both painted images using paint, but their techniques (and the results they achieved) were very different!
Chuck Close. Self-Portrait (2000-01). ARTSTOR
The use of new media in art has given rise to the idea that NEW MEDIA can be considered as a different type of art.
Example: Performance art uses the artist's body as the material or medium.
Example: Environmental art, often using items found in nature, can be considered alongside traditional media such as sculpture or painting. (Art Term: Medium).
Temporary sculpture made from stones.
Andy Goldsworthy. (1985). "Broken pebbles/scratched white with another stone, St. Abbs, The Scottish Borders". ARTSTOR.
Georges Seurat (1859-91) "A Sunday Afternoon on the Island of La Grande Jatte" ARTSTOR.