superposition

/S UW0 P ER0 P AH0 Z IH1 SH AH0 N/
noun
  1. 1

    The placing of one thing on top of another.

  2. 2

    The deposition of one stratum over another; the principle that in a series of sedimentary strata, the lower strata are the older.

  3. 3

    The situation in quantum mechanics where two or more quantum states are added together (superposed) to yield another valid quantum state.

Source: https://en.wiktionary.org/wiki/superposition