English
The minimum of a and b equals a if a < b, otherwise it equals b (i.e., min a b = if a < b then a else b).
Русский
Минимум(a,b) равен a, если a < b, иначе равен b.
LaTeX
$$$ \\min a b = \\begin{cases} a, & a < b \\\\ b, & \\text{иначе} \\end{cases} $$$
Lean4
theorem min_def_lt (a b : α) : min a b = if a < b then a else b := by rw [min_comm, min_def, ← ite_not];
simp only [not_le]