A
binder is any material or substance that holds or draws other materials together to form a cohesive whole mechanically, chemically, or as an
adhesive. Often materials labeled as binders in different proportions or uses can have their roles reversed with what they are binding. An example is straw helping to mechanically
bind clay together as in the building material
cob, and clay as an adhesive helping to
bind straw together as in a natural insulation.