superposition

(noun) (geology) the deposition of one geological stratum on another.

(noun) (geology) the principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest. Synonyms: principle of superposition, superposition principle.

(noun) (geometry) the placement of one object ideally in the position of another one in order to show that the two coincide.

(noun) the placement of one thing on top of another.