Assertion: substitution | /r/HasProperty | idempotent
Facets:
Source sentences:
text: The substitution { x ↦ y+y } is idempotent, e.g. ((x+y) {x↦y+y}) {x↦y+y} = ((y+y)+y) {x↦y+y} =
text: A substitution σ is called idempotent if σσ = σ, and hence tσσ = tσ for every term