concretion

(noun) the formation of stonelike objects within a body organ (e.g., the kidneys).

(noun) a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body. Synonyms: calculus. Example: "Renal calculi can be very painful."

(noun) an increase in the density of something. Synonyms: compaction, compression, densification.

(noun) the union of diverse things into one body or form or group; the growing together of parts. Synonyms: coalescence, coalescency, coalition, conglutination.