A nodule describes similar aggregation of cells or particles in a number of scientific fields:

• In medicine it refers to a small aggregation of cells. Nodules may form on tendons and muscles in response to injury. The vocal cords may also develop nodules. Nodules are normally benign and often painless although they can affect the functioning of the organ.

• The term is used in geology to refer to a small knobbly rock or mineral cluster.

• The term in also used in plant biology to describe root outgrowths also called root nodules . These are formed on the roots of legumes and house symbiotic bacteria that fix atmospheric nitrogen and provide it to the plant in exchange for carbon.