Def pg.104 For set 𝐴⊂ℝ, if 𝑐∈ℝ is cluster point, we can say (∀𝜀>0)(∃𝑥≠𝑐∈𝐴)|𝑥−𝑐|<𝜀 Basically, for common Metric Space, it’s equivalent to the limit point.