accretion

(noun) an increase by natural growth or addition. Synonyms: accumulation.

(noun) something contributing to growth or increase. Examples: "He scraped away the accretions of paint." "The central city surrounded by recent accretions."

(noun) (astronomy) the formation of a celestial object by the effect of gravity pulling together surrounding objects and gases.

(noun) (biology) growth by addition as by the adhesion of parts or particles.

(noun) (geology) an increase in land resulting from alluvial deposits or waterborne sediment.

(noun) (law) an increase in a beneficiary's share in an estate (as when a co-beneficiary dies or fails to meet some condition or rejects the inheritance).