If R is an integral domain, then a field of fractions F can be defined which naturally contains R. The field F is the set of equivalence classes of (r₁,r₂), where r₁,r₂ ϵ‎ R and r₂ ≠ 0 under the relation (r₁,r₂) ∼(s₁,s₂) if r₁s₂ = r₂s₁. The equivalence class of (r₁,r₂) can be identified with r₁/r₂, so that (r,1) can be identified with rϵ‎R. The field of fractions of ℤ is ℚ with (4,8) and (–2,–4) both identified with ½.