In this chapter, we study conditions of separability for Orlicz spaces LΦ. We consider Young classes YΦ, the subspaces HΦ, and their embeddings HΦ ⊆ YΦ ⊆ LΦ. We show that the equality HΦ= YΦ = LΦ is equivalent to separability of LΦ. This and other equivalents of separability studied earlier in Chapters 6 and 7 can be expressed in term of an Orlicz function Φ. The (Δ2) condition is described to this end in detail.