difference equation

Short definition from Wiktionary

Noun

1. 1
   An equation involving an ordered sequence of real numbers (a_nₙ₌₁ ᪲) and some of its differences, where the first difference is defined as Δ(a_n)=a_n+1-a_n, and the kᵗʰ difference is defined recursively as Δᵏ(a_n)=Δᵏ⁻¹(a_n+1)-Δᵏ⁻¹(a_n),.
2. 2
   more broadly, any recurrence relation