substitution
noun OPAL W
  /ˌsʌbstɪˈtjuːʃn/
  /ˌsʌbstɪˈtuːʃn/
[uncountable, countable]- an act of using one person or thing in the place of another- Two substitutions were made during the game.
- substitution of A for B the substitution of low-fat spreads for butter
- substitution of B with A the substitution of butter with low-fat spreads