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

• In medicine, a nodule refers to a small aggregation of cells.

• In geology, a nodule refers to a small knobbly rock or mineral cluster. (For example, Manganese nodule)

• In plant biology, a root nodule is a root outgrowth formed on the roots of legumes and house symbiotic bacteria that fix atmospheric nitrogen and provide it to the plant in exchange for carbon.

Nodule